Faucet Basics: Part 2 Faucet Valves & Cartridges
From the point of view of the mechanics involved, a basic faucet is nothing more than a valve that controls and directs the flow of water through a tube. The main components are the valve itself, a body to contain the valve, a handle to operate the valve, and a channel through which the water flows.
The sole function of the valve is to control the water passing through the faucet. It turns the water on and off and limits the amount of water flow which can range from a trickle to a deluge.
It all sounds rather simple in the abstract, but it took most of human history to invent a valve that controls water effectively and is reliable and durable enough for use in a household faucet. In fact, the faucet valve has been around for just 150 years.
To put that in perspective, my grandmother late in her life had a working faucet in her kitchen but in her youth she and her siblings had the chore of hauling water to the kitchen in buckets.
If you have ever had to haul water in buckets, then you know how much easier the faucet valve has made our lives.
The faucet valve, therefore, should always be the best valve you can afford, and valve reliability should be the most single important consideration when buying a faucet.
A valve consists of two parts. The moving part or "stem" attached to a handle and the fixed part or "seat". To shut off water flow, the moving part is pressed against the fixed part until the water stops.
A Brief History of Faucet Valves
In early faucets, the valve stem moved up and down inside the body of the faucet itself in early faucets just as shown in the illustration above.
The modern valve, however, is usually built into a removable carrier called a cartridge which is inserted into the body of the faucet. Any wear on the valve takes place inside the cartridge, not inside the body of the faucet.
If the valve fails, the cartridge can easily be replaced, restoring function to the faucet. Before removable cartridges, the faucet body would have needed to be re-machined or the whole faucet replaced.
Early faucets delivered hot and cold water separately – one faucet for hot, the other for cold. Temperature mixing occurred outside the faucet in the sink or tub.
These can be dangerous (the hot water can be scalding hot) and are rarely seen today in North America outside historical restorations. (In the UK, however, they are still very common.)
The modern faucet is a mixing faucet, invented by Canadian, and patented in England in 1880. It blends hot and cold water inside the body of the faucet – out of harm's way – before delivering it to the sink or tub.
Campbell's mixing faucet was the model for faucets for over sixty years, from the 1880s to the 1940s when the next big step in valve design was introduced.
Do these faucets look familiar?
Chances are one of them does. You probably owned one, or, depending on your age, your parents or grandparents did.
These are the original single-lever kitchen faucets introduced in the 1940s and '50s: the Moen 8710 (top) and Delta 100, featuring the revolutionary washerless cartridges that made single-handle faucets possible.
These are some of the best-selling faucets of all time and many thousands are still in service.
The Moen 8710 was only recently discontinued, but the classic Delta 100 is still being made and is widely available for about $80.00.
This was the "washerless" faucet valve invented independently by Alfred M. "Al" Moen and .
Al Moen was the first up to bat. His earliest version of what would become the sleeve cartridge valve was created in 1939.
He worked on improved versions for most of the next six years, throughout his wartime service with the U.S. Navy and beyond, creating and discarding ideas for a single handle faucet valve before he came up with a reliable working model.
After his discharge in 1945, he persuaded Ravenna Metal Products of Seattle to finance and produce the first single-handle faucet using the Moen valve. This faucet, introduced in 1947, became the nucleus around which the modern Moen faucet company was built.
Landis Perry also worked on his version the valve during his wartime service with the military. He applied for a patent on his "mixing valve" as soon as he left the service in 1945. The application bounced around the patent office for seven years before a patent was finally awarded in 1952 (U. S. patent 2592062).
Alex Manoogian, then president of Masco Screw Products, licensed the valve from Perry and founded Delta Faucet to make single-handle faucets using the new valve. Just four years after Delta's first single-handle faucet was introduced to the American public, Delta sales topped $1 million.
valves were a giant step forward in the 1940s and '50s.
These valves still needed to compress rubber seals to shut off the water but the new design eliminated the twisting motion that wore out rubber seat washers so quickly. The rubber seals in washerless valves could last five years or even longer as the technology improved.
The newest technology, ceramic disc valves, eliminate friction against rubber entirely. Water flow is controlled by nearly indestructible ceramic discs, not rubber seals. Ceramic disc cartridges typically last ten years or more without maintenance, and some super ceramic cartridges will last a lifetime.
Ceramic disc valves were invented independently by two American faucet companies: which separately patented versions of a ceramic disc cartridge in the 1970s.
The tecnology was alow to catch on in North America, but almost immediately swept Europe where faucet companies quickly adopted and improved upon ceramic valves. By the late 1980s, luxury European faucet from companies like were becoming serious competition, forcing American companies to finally switch to ceramic technology.
Early Faucet Valves
The earliest type of valve was a device that pressed a plug into a seat to stop water from flowing and retracted the plug to allow it to flow again.
For much of the first century of faucet development, there were two competing technologies: the compression valve that used a screw mechanism to control the plug, and the Fuller valve that controlled the plug with a lever and cam.
The first practical compression valve was invented in 1845 by John Guest, a plumber, and the brothers Richard and Edward Chrimes Jr. owners of a foundry in Rotherham, England named Guest & Chrimes Brassworks. It manufactured faucets (which were variously called sluice cocks, hydrants, and taps) and other devices that included the valves until its closing in 1999.
The earliest compression valves used a stack of leather washers as a plug. Turning the handle of the faucet raised and lowered a stem. The plug – called a seat washer – at the base of the stem, was pressed into a metal (usually brass) seat until water flow stopped. To start water flowing again, the plug was retracted by turning the screw the other way.
It was a great improvement over then existing water control technology that consisted of some version of driving a plug or "bung" into the end of a pipe to stop the flow of water, often with a mallet, and removing it to start water flowing again.
It made bringing water into the house practical because water could be precisely and reliably controlled. The Guest & Chrimes valve not only started and stopped water flow, it also regulated the volume of water – a feature the old plug-and-mallet technology did not have.
The screw action to open and close the valve worked well but also wore out the leather washers fairly quickly by repeatedly grinding them into the seat.
Even after the switch from leather to rubber washers, the problem of rapid washer deterioration continued, abated only somewhat by improvements in washer technology.
The Fuller Valve
Fuller's invention, patented in 1879, used an eccentric cam attached to a handle to press a grape-sized rubber plug  into the seat, shutting off the water.
Unlike the compression faucet that operated against the stream of water, the Fuller valve worked with water pressure to improve the seal. Since the cam mechanism did not grind the rubber plug to stop water flow, the mechanism lasted much longer between repairs.
Precise control of flow volume was tricky, however. The cam required only about a half turn to bring the flow of water from off to full-on, so regulating the volume of water required a deft touch.
Moreover, according to generally accepted plumbing lore, it could take a lot of force to squeeze the ball into its seat hard enough to stop water flow, especially as the ball wore down, so large lever handles were common to provide the needed leverage.
Brian Marrone, whose company, Brians Plumbing Works in Gladstone, Oregon, repairs and restores original fuller faucets, disputes this traditional view.
The large handles, he says, were ornamental – a Victorian-style preference – not functional.
As the Victorian era gave way early in the 20th century to the Arts & Crafts movement in interior design, large levers disappeared. The lever handles on Fuller faucets were no larger than those found on compression faucets.
According to Brian, extreme force applied to the lever would deform the eccentric post at the end of the main stem, damaging the faucet. But, he writes, that he seldom finds any deformation of this component:
"I have worked on many Fuller valves at this point and most of them do not have terrible wear on the stems. The balls are all corrupted and the seats need to be honed but the stems are, more often than not, in fair condition."
Compression Valves Today
In the end, the Guest & Chrimes screw-type compression faucet won the day. Better design and improved rubber made compression faucets more reliable as time passed. They were also less expensive than Fuller designs.
By the turn of the 20th-century compression valves that required several turns to reach maximum water flow were being replaced by newer models that required no more than a quarter turn. This put much less twisting force on the compression washer, further reducing wear and extending the life of the washer.
Fuller ball valves, despite several improvements in the technology over the years, started to die out in the 1920s and are no longer to be found. Even replacement parts are becoming hard to find .
Compression valves are still widely used, just not in home kitchens or baths.
Outdoor faucets are called "bibcocks", "spigots", "wall hydrants", "hose hydrants", "garden valves", sillcocks, or "hose bibbs" – depending on where you live in North America – just a little plumbing trivia, for fun.
The outside faucet attached to your house probably has a compression valve because it withstands the winter freeze better than any other valve technology.
Compression valves are also the preferred valve in restaurant, hotel, and institutional kitchens where the ease of replacing the compression washer outweighs the nuisance of having to replace it more often.
A busy Arby's or IHOP kitchen cannot shut down for a day waiting for a replacement ceramic cartridge to arrive by FedEx, it needs to be able to get a malfunctioning faucet working again right now, and replacing the compression washer – which typically takes about 10 minutes and uses parts that every plumber always has tucked in his or her toolbox – usually does the trick.
All manufacturers of commercial faucets like that specialize in heavy-duty faucets for restaurants, hotels, and medical facilities engineer their heavy-duty faucets around very durable quarter-turn compression valves as the standard water-control technology.
These valves, while the direct descendants of the Guest & Chrimes original, are modern incarnations with durable synthetic seat washers and removable seats.
Some, however, have been unchanged for most of a century. The venerable Quaturn® compression valve, for example, used in faucets manufactured by the Chicago Faucet Company has been in continuous use for over a century and shows no sign of going away any time soon.
The Washerless Revolution
The compression valve had a long and impressive run as the preferred valve in household faucets. It was king until well into the 1960s, and every homeowner learned how to replace a valve washer (See the sidebar. The Repair of Leaking Faucets) – a task that was required every year or more often as the valve seat wore.
If you delayed in replacing the washer, the valve seat might be scratched or damaged, and honing the seat back to its original pristine smoothness might require the services of a plumber or at very least a DIY-er with a hone and precise touch.
The Moen Cylinder Valve
The washerless valve completely changed the plumbing landscape, making the single-handle mixing faucet possible.
Before the Moen valve, all faucets were two-handle faucets. The hot side and cold side were operated separately.
With the Moen cylinder valve, hot and cold could be controlled with a single handle. Today 40% of all faucets sold in North America are the single-handle type and in the kitchen, that percentage jumps to over 60%.
Al Moen's washerless valve eliminated the rubber compression washer entirely – it was washer-less. Although it still used rubber (and later, Silicone or Nitrile) seals and O-rings, the seals are not twisted and ground down by the operation of the faucet, which made them last much longer.
The Moen Faucet Revolution
- The sanitary vitreous china toilet tank that replaced the tin-lined wood tanks then in use (1903),
- The integrated apron alcove tub (1911) – the most common tub type in use today,
- Emerson Electric's In-Sink-Erator disposer invented by John W. Hammes (1927), and
- The Watts pressure relief valve invented by Joseph Watts that made safe water heaters possible (1930).
The Moen valve is a cylinder. The faucet handle moves the cylinder up and down inside the faucet to control the volume of water and rotates it from side to side to control the water temperature. This is done by aligning strategically placed holes in the cylinder with matching holes in the faucet body. When the holes are aligned, water can flow, when not aligned, water stops flowing.
When the handle is rotated left, the hot water inlet is aligned so hot water flows, when rotated right, the cold water inlet is aligned, and cold water flows. In any position other than far left or right, the hot and cold water is mixed to varying degrees of warm water.
"Moen motion" has become the standard for all single-handle faucets made since.
No matter the style, source, brand, or manufacturer of a single-handle faucet, moving the handle up or back turns the water on – the further up or back the handle, the more water you get. Down or forward turns it off. Right delivers cold water and left supplies hot water.
As a consequence no one has to relearn how to operate his o her faucet every time he or she buys a new one – they all operate the exact same, Moen, way.
Moen faucets were the "modern" feature of many post-war kitchens and baths. (See Post-war Housing Styles for more information on the origin of the modern kitchen.) But, not without a fight. Plumbers, who are naturally conservative folk (as befits a trade whose work is expected to last decades if not centuries), distrusted this new-fangled device and were slow to adopt it.
Moen geared up its marketing machinery and with discounts, incentives, and some clever advertising targeted at housewives – the ultimate arbiters of what does and does not go in a kitchen – persuaded plumbers to try it. They did, and they liked it.
At least in our town, Lincoln, Nebraska, if you leave it up to the Plumber to select your faucet, you will probably get a Moen. Plumbers like the fact that a Moen faucet almost never breaks, eliminating costly and annoying call-backs.
Seal and O-ring replacement is made easy because the cylinder can be removed and serviced as a unit. Quality is determined by the materials used in the cartridge: plastic, brass, or stainless – although we have not seen stainless in a Moen cartridge in a long while. Evidently, brass works just as well and is a lot less expensive. Both metals outlast plastic by a country mile.
If the cylinder does develop a drip, seal replacement is a 15-minute repair using a kit available at nearly any hardware store. Or, just replace the whole cartridge.
A Moen washerless cartridge fits any Moen faucet that requires a washerless cartridge, and with Moen's lifetime warranty, replacement cartridges are free. Just dial 1-800-BUY-MOEN or visit your local hardware or plumbing store.
The store may ask you to fill out some warranty paperwork but, otherwise, it's a no-hassle process. (To see how simple it is to replace a Moen cartridge, watch this video).
As a result of its marvelous new valve, Moen grew from a niche player in the faucet biz to one of the two largest faucet companies in America ( is the other one).
Delta Ball Valve
The ball valve was Delta's answer to the Moen washerless cartridge. It was not, however, as Delta sometimes claims, a Delta invention.
patented it in 1952. Delta bought the patent and its engineers cleaned up the design a little to make it easier and cheaper to manufacture but otherwise left it pretty much alone.
It works just like a Moen washerless valve – in fact, it really is just a Moen valve configured as a ball rather than a cylinder. But, the ball shape was just different enough to enable Delta to squeeze around Moen's patent – much to Moen's irritation.
Rotating the handle forward and back lines up different slots to control water volume from trickle to torrent, and moving it right and left controls water temperature, just like the Moen valve.
It was a definite improvement on the Moen cartridge. It had fewer parts. It was much smaller, which simplified faucet design, and was easier to maintain. In place of the four o-rings required for the Moen cartridges, it used two rubber seals that wore out more slowly and were easier to replace.
Early ball valves were brass, current models are stainless steel and nearly indestructible. Delta boasts a failure rate of less than one in 100,000 units (0.001%). But, Delta also makes a "Thrifty" ball cartridge for its low-end faucets (also used in faucets) out of plastic. In this case thrifty is not nifty. The ball is very susceptible to damage from mineral build-up that can actually score the ball, rendering it useless. It's easy to replace but why buy the problem?
Even before Delta's patent on the ball valve expired, it was widely copied. Delta had to sue several other faucet companies for counterfeiting its proprietary valve.
Now that the patent is expired, it is even more widely copied and popular as the valve used in a great many, if not most, economy faucets including some of Delta's utility faucets and faucets targeted at multi-faily dwellings such as faucets from Kissler, Co. and faucets from Interline Brands.
The ball valve is a very simple device, so most of the copies work well. However, be aware that if you purchase a ball valve replacement for a Delta faucet from any source other than Delta, there is no guarantee that it will be a genuine Delta ball.
The Ceramic Disc Cartridge Valve
The Moen cartridge seals off water flow with several vulnerable rubber o-rings that eventually wear out and fail. The Delta ball design needed just two seals but friction against the rotating ball would eventually wear them out – especially as the ball becomes encrusted with sand-paper-like mineral deposits (which is inevitable in most parts of North America).
Replacing them is very easy and well within the ability of any handy homeowner (See How to Repair a Leaky Faucet for a video illustration) but, obviously, eliminating all fiction against rubber seals would be a great advance in leak-proof technology.
And, that was the advance implemented by in the ceramic disc cartridge valve.
The old, pre-breakup, American Standard Companies  was a pioneer in ceramic technologies. It had been manufacturing ceramic bathroom fixtures since the 1880s, so it seems entirely natural that it should put its industrial ceramics expertise to good use by creating a faucet valve that used nearly indestructible ceramics rather than rubber to control water flow. But, evidently, the process was not as straightforward as all that.
The company, then trailing both Moen and Delta in valve technology, first looked at metal discs to control water flow. But, its engineers were suspicious of metal, fearing that it would not be robust enough for the harsh and gritty world of faucet valves and at risk of corrosion.
They decided to replace the metal discs with a technical ceramic made with a dash of aluminum oxide (alumina) – still the standard for ceramic discs today. After much experimentation and development, the company received patent number US 3,810,602 A for a "ceramic disc faucet" in 1974.
Wolverine's very similar valve also received a patent: No. 3,780,758 issued in December 1973.
The ceramic disc valve uses a pair of ceramic discs that rest against each other to control water flow. The mechanism of the valve was enclosed inside a removable housing or cartridge.
The discs are polished to near-perfect flatness. The space between the closed discs is smaller than a molecule of water, which is why water cannot flow between them when they are closed. The technology eliminated friction on rubber rings and seals and vastly extended the service life of the valve.
Ceramic discs are very hard – even harder than mineral deposits, which makes them ideal for the rough and gritty environment of a faucet valve. They resist the effects of hard water better than any other material. Fired at temperatures over 2,000°F, these discs are also unaffected by the hottest household water, unlike the rubber or silicone washers and o-rings that can soften.
The cartridge that contains the valve mechanism is designed to be easily replaced. Replacement is rare, however. An ordinary run-of-the-mill ceramic disc valve easily lasts 5-10 years, and some of the newer super valves are estimated to have a service life of nearly 770 years. (No, that is not a typo.)
But, ceramic cartridges are not without problems. The discs fit so close together that they are actually sticky and sometimes hard to move. To ease movement, most ceramic discs are coated with a durable water-insoluble lubricant. Over time, however, the lubricant can be scrubbed away by the friction of water passing between the discs, which makes the faucet harder to operate, and in extreme cases, it ceases to operate altogether.
Ceramic cartridge makers have improved lubricants over the years, searching for formulas that are more durable and last longer. But, there is a limit to this technology, and no matter how good the lubricant is, the abrasive effect of water and minerals in the water will ultimately wear it away. It may take longer. It may, in fact, take years. But it will happen. So, the next step in the ever-evolving ceramic disc technology is to eliminate the need for lubricants by making the discs slicker so they won't stick to each other.
One approach is to coat the ceramic discs with a material that is slicker and even harder than the discs themselves. Diamond-like carbon (DLC) is one such material. A thin coating deposited on ceramic discs using a technology called physical vapor deposition is enough to not only improve the disc's hardness but create a very "slippery" surface that slides freely without the need for lubricant. Another approach, used in Delta's Diamond Seal Technology® cartridges is to coat one disc with a diamond powder that not only makes the discs slide more easily, but also continuously polishes the uncoated disc so it remains absolutely flat.
Types of Ceramic Disc Valves
Ceramic disc valves mimic the valve technologies they are designed to replace. Single-function stem cartridges are used in place of compression valves, and dual-function mixer cartridges replace Moen cylinder and Delta ball valves in single-handle faucets.
Single-Function Stem Cartridge (or Headworks) for Two-Handle Faucets
Single-function or stem cartridges, sometimes called the headworks or just "stems", are used with two-handle faucets. They exactly duplicate the action of the older compression valves.
Each handle of the two-handle set is attached to a separate cartridge, one for hot and one for cold. Each valve controls only water flow. Temperature mixing is accomplished by increasing or decreasing the flow of hot and cold water inside the faucet. Increasing the flow of hot water or decreasing the flow of cold water makes the mix warmer. Decreasing the volume of hot water or increasing cold water flow makes the mix cooler.
The cartridges are usually not interchangeable. To prevent errors in installation a hot-side cartridge is engineered to fit only on the left side of the faucet and the cold side on the right. There are also likely to be slight differences in the materials used depending on whether it is a cold side or hot side cartridge. (For a well-done and helpful video on the difference between a compression cartridge and a ceramic cartridge, see T&amb;S Brass Cartridges.)
Dual-Function Mixing Cartridge (or Mixer) for Single-Handle Faucets
A single-handle faucet uses a dual-function mixing cartridge – "dual-function" because it controls the temperature of the water as well as the volume of water flow.
Temperature mixing occurs inside the cartridge itself before the water is delivered to the faucet. One disc, attached to the handle moves up and down to turn the water on and off; and left and right to align slots in the ceramic discs to allow hot and cold water to mix – just like the Moen cylinder or Delta ball cartridge it replaces.
Ceramic Cartridge Materials
A ceramic cartridge has three main parts: the ceramic discs, a stem, and a housing or case.
The stem is attached to the faucet handle on one end, and to one of the ceramic discs on the other. Moving the handle to operate the faucet moves the stem which operates the "movable" disc. The other "fixed" disc is bonded firmly to the housing. The case or housing holds all the parts together.
The movable parts of the cartridge – the stem and discs – are the most susceptible to wear and damage. These need to be strong. In the best cartridges, the stem is brass or stainless.
In economy cartridges it is plastic. Plastic is not as durable as metal and can be more easily damaged by the repeated twisting forces (or "torque" in engineer-speak) applied when the faucet is operated. Enough torque applied to a jammed cartridge can twist a plastic stem completely off.
A housing made of brass, aluminum, or stainless steel holds up very well. All of the better single-function cartridges for two-handle faucets are metal. Some stem cartridges used in economy faucets, however, are encased in plastic housings. The housings in almost all dual-function mixing cartridges are also plastic.
Plastics used in ceramic cartridges, primarily polyvinyl chloride (PVC), polyoxymethylene (POM), and nylon have been greatly improved over the years, and today function very well most of the time. Some plastic used in cartridge cases is truly tough stuff. CeramTec of Luft, Germany uses an advanced plastic developed by EMS-Grivory for use in, among other places, outer space. If it will survive space, it is a safe bet that it will survive in your kitchen.
What If a Cartridge Collar Fails?
One Homeowner's Experience
Well that was strange. A few days ago, I was innocently relaxing in my living room watching tv, when I heard a sudden rushing sound coming from the nearby bathroom. I dashed into the bathroom to see what had happened, and was surprised to see that the hot water handle on the bathroom sink faucet had blown completely off and a firehose-strength stream of hot water was quickly flooding the room!
After getting the flood under control by closing the shutoff valve, I took a close look at the faucet to see what the hell had happened. Close examination of the valve showed that a threaded plastic collar holding the valve's cartridge in place had cracked. The collar thing seemed rather poorly designed and weak, considering that it appeared to be the only thing holding the faucet together against the water pressure. I said a few choice words about the designer (probably chinese) of this lousy faucet, and thanked my lucky stars that I was home when the event happened. This sort of thing can cause tens of thousands of dollars of flood damage if not stopped quickly.
At any rate, I suggest you take a look at your household faucets and make certain they have a solid valve design that won't suddenly explode if a weak plastic part fails. MY problem faucet was installed by a contractor a few years ago, and was probably selected for its cheap cost. The faucet looked good, but the handles were made of chrome plated plastic, which should have been a clue to its low quality. No brand name was visible on the faucet, so I don't know who made it. update - appears to be an American Standard (Made in mexico!)
But, plastics are complex chemical mixtures that require very precise processing. If anything goes wrong, the result is likely to be a brittle or fragile plastic that will not hold up inside a faucet. Most of these errors are caught inside the factory, and never see the light of day. But not all.
In the example shown in the sidebar Autopsy of a Failed Plastic Cartridge, a minor flaw in the chemistry of the plastic allowed hot water to deform a thin flange at the bottom of the cartridge housing. This permitted hot water entering the cartridge to mix with cold water irrespective of the position of the handle causing warm water to flow through the cartridge continuously. The plastic used in cartridges is supposed to withstand the heat of household water without deforming. This one did not.
To offset the potential of plastic housings to deform in use, they are often enclosed in metal carriers. This is true, however, primarily of premium faucets like . in less expensive faucets, the carriers are plastic. Plastic carriers combined with plastic housings are more at risk for deformation caused by aggressive operation of the faucet or careless installation.
The Super Cartridges
has trumped the traditional ceramic cartridge makers with its new Diamond Seal Technology® (DST) dual-function ceramic super cartridge. One disc in the two-disc set is diamond coated using a process that creates microscopic diamond-shaped pyramids on the disc.
Delta says the diamond coating keeps the discs absolutely smooth since the coated disc continuously polishes the other disc so they always mesh perfectly. It also continuously grinds away any mineral deposits that may insinuate themselves between the discs. The more you use it, the smoother it gets, says Delta, which claims that the cartridge will last up to 5 million rotations (or about 770 years in the average kitchen faucet, 20 to 30 times the lifespan of a standard ceramic cartridge). (But, if you ever need to change the cartridge, Delta has a video for that, and the replacement is free from Delta to the original owner for the owner's lifetime.)
The DST technology is now available on nearly all Delta and Brizo faucets.
Delta's is not the only super technology in use, however. Another proven approach is to coat both ceramic discs with a material that is very slick and also very hard. One of these is diamond-like carbon (DLC), one of the hardest materials known to man (hence the "diamond-like" in its name).
As an example of how hard it is, stainless steel coated with DLC just two microns thick resisted abrasion in laboratory tests 4,000 times longer than uncoated steel (1 week vs 85 years).
A very thin (measured in microns) coating deposited on the cartridges using physical vapor deposition (PVD) technology is enough to not only improve the disc's hardness but create an exceptionally "slippery" surface that slides freely without the need for lubricant.
Faucets known to use DLC coating on their ceramic discs include which uses a super mixer cartridge made by Kerox, Kft" in all of its single-handle faucets. Some cartridges made by Flühs Drehtechnik, GmbH use a similar technology.
In2aqua estimates that its proprietary PVD+™ DLC-coated discs will last 10 times longer than uncoated discs. Based on independent laboratory tests that estimate may be a little on the conservative side. After putting the discs through 4 million consecutive off/on-hot/cold cycles over 90 days, they showed no observable wear. Four million cycles are equivalent to about 550 years of use in an average home kitchen. We think the odds are very good that PVD+ discs will operate for the entire lifetime of the faucet without replacement.
Ceramic Cartridge Testing & Certification
Every part of a faucet undergoes rigorous testing before it is certified to North American standards. No part, however, is tested with more rigor that the faucet cartridge. The testing standard ASME A12.18.1 requires stress testing to many times its normal use in your home.
The usual domestic water pressure is between 40 and 60 pounds per square inch (psi). This may not sound like much, but consider this: 50 psi is over 6.5 tons of pressure per square foot. If this much weight were placed on the floor of your house, it would instantly collapse. Yet, your faucet cartridge contains this much pressure 24-7-365 and is expected to do so ear after year without a drop of leakage.
But, that's not the whole pressure story. When you shut your faucet off suddenly, water pressure can surge to 200 psi, that's nearly 15 tons per square foot – enough fore to squash an M-1 battle tank like a bug.
Why a cartridge can stand up to this level of stress is in no small part a function of how strenuously faucet cartridges are tested.
A cartridge is put through a lot of different tests. It must prove itself free of lead and other substances that can harm you, even in small quantities. These include cadmium, arsenic, mercury, several other heavy metals, and a myriad of harmful chemicals. But, the tests that are most important to the longevity of the cartridge are the life-cycle and pressure tests.
The pressure test is what is called a hydrostatic shock test. It emulates a very dramatic pressure surge. The test requires the cartridge withstand a pressure of 500 psi for 1 minute without distortion or failure. If you ever get a surge of 500 psi in your home plumbing, most likely a lot of pipes would burst.
If a cartridge fails the test, the failure is usually dramatic. Typically the cartridge just explodes. But, failures are rare. Why? Because manufacturers make absolutely certain the cartridge will pass by testing it thoroughly before submitting it for certification.
The standard life-cycle test for cartridges requires operating the faucet through 500,000 cycles under 60 psi of water pressure without a single failure. At one cycle per second, the test takes six 24-hour days to complete. Five hundred thousand cycles are equivalent to about 70 years of ordinary kitchen faucet use.
So, you may ask, if faucet cartridges are that tough, how is it that mine leaked after just a few years? Good question and we have a good answer.
It's not because cartridge manufacturers cherry-pick on their best cartridges for testing. Testing laboratories are on to that trick and usually pick cartridges for testing right off the assembly line.
The real reason is dissolved minerals in tap water. Faucets are tested in pure, distilled water. But, tap water is often full of minerals. Mineral (or lime-scale) build-up inside the cartridges can dramatically shorten cartridge life. Delta's Diamond Seal Technology super cartridge overcomes this problem by embedding diamond dust in one of the two ceramic disks in its cartridges to continuously grind away any mineral build-up. Most other cartridges do not have this feature, and won't until Delta's patent expires. Until then, figure on replacing your cartridge every ten years or so.
Ceramic Cartridge Manufacturing
Some faucet companies use proprietary cartridges that they often design and engineer themselves.
But, while faucet companies may assemble their own cartridges, we don't know of a single faucet manufacturer that actually makes its own ceramic discs. Making a ceramic disc requires technologies and expensive specialized ceramic manufacturing machinery that metal-working faucet companies don't usually own.
Ceramics are, of course, the "space-age" material of the 21st century, used in everything from bullet-proof vests to Space Shuttle heat shields. We're not sure how a material that has been around for 10,000 years or so has suddenly become "cutting edge", but there it is. Long before recorded history some pretty good pottery was being made, and pottery, for those that don't know, is a form of ceramics.
Many of the companies that now manufacture faucet discs started out in some other branch of technical ceramics. CoorsTek, the American ceramics manufacturer founded by Adolph Coors (yes, of Coors Beer fame), makes ceramic discs used in any number of proprietary faucet cartridges but is also makes ballistic armor, ceramic insulators, automobile components, and oven-safe ceramic cookware. (It does not, however, make beer – arguably the most important Coors product. That's Coor Brewing Company.)
Kerox Kft, the Hungarian technical ceramics manufacturer that makes ddual-function mixing cartridges famous for their reliability, started out making dental ceramics, and still does. Its dentures are in use all over Eastern Europe.
Roughly the same technology is used to make all technical ceramics. The main difference is the composition of the material used for each product. A ceramic disc for a faucet cartridge usually includes a special form of clay called kaolin, feldspar, and quartz or silica but also a dash of aluminum oxide (alumina) for high strength and hardness, an additive not usually found in ordinary pottery.
The mix is shaped into a disc blank in a high-pressure press. The rough blanks are then fired in a furnace at a very high temperature for 18-24 hours to harden the ceramic and fuse the particles in the mix together, then cooled for up to several days.
The cooled discs are finished by grinding the meeting surfaces nearly perfectly flat, and then polishing them in stages: a rough polishing followed by a second, finer, polishing and, for better discs, a third, super fine, polishing.
(For those unfamiliar with how ceramics are made, see Porcelain vs. Ceramic Tile: What is the Difference?)
The difference between good and not-so-good ceramic discs is the quality of the materials used and the care with which the discs are manufactured.
Mixtures high in alumina produce harder discs, and alumina with a fine crystalline structure polishes to a smoother finished surface than alumina with coarser crystals. Some manufacturers add a little zirconia to the mix for even greater strength. Zirconia is very hard. Fused zirconia is nearly as hard as diamonds (78 on the Rockwell B scale, diamonds, the hardest known material, are 100).
Better discs also tend to be fired for a longer period of time which fuses more of the material. The best discs are very hard, testing at 62 on the Rockwell D scale, while economy discs top out at about 48. For comparison, tool steels used to make chisels and hardened drill bits usually test at Rockwell 55 to 66 (on the A or D scale), so ceramic discs are tough stuff.
The Standardization of Dual-Function Ceramic Cartridges
Single-function ceramic stem cartridges, intended to replace compression cartridges, were designed originally to duplicate the size and configuration of the compression cartridges they replaced (see the illustration at Compression vs. Ceramic Stem Cartridges). In consequence, they were more or less standardized right from the beginning.
Dual-function cartridges, intended to replace Moen and Delta washerless valves were not. There were no standard washerless valves. The Moen cylinder valve and Delta ball valve were very different. American Standard's ceramic cartridge did not try to emulate either product, but struck off on its own, designing a ceramic valve to best carry out its functions. The resulting cartridge looked nothing like either the Moen or Delta valve.
Later ceramic cartridges copied the American Standard design, but not exactly, and for the first fifteen years of ceramic cartridge history, the size and configuration of dual-function mixing cartridges were left up to the individual manufacturers. They were not interchangeable. One manufacturer's cartridge could not be used in another's faucet.
If a faucet maker used a particular dual-function cartridge in its faucets, it was stuck with that cartridge unless it redesigned and re-engineered its faucets to accept another manufacturer's cartridge – an expensive proposition.
Standardization began around 1980 when Galatron Plast S.p.a., an Italian technical ceramics company, developed two basic designs for ceramic cartridges that were simple, inexpensive to manufacture and very reliable.  Other manufacturers took note.
The designs were widely copied by European cartridge makers, among which were Kerox Kft in Hungary, CeramTec, in Germany, which makes the popular Triduon® cartridge, and Hydroplast, the Italian manufacturer.Asian cartridge manufacturers soon followed, including Sedal S.L.U. in China, and Kuching International, Ltd., the manufacturer of the widely used KCG cartridge, and Geann Industrial Co., Ltd., both in Taiwan.
Not only has the industry settled on more or less de facto standard cartridge designs, but it has also developed more or less standard sizes. Today a faucet designed for a 35 mm cartridge with a flat base can use a 35 mm flat-base cartridge from any of several manufacturers. And, faucet manufacturers have learned to mount cartridges into carriers rather than directly into the body of the faucet. Changing cartridges, then, may mean redesigning the carrier but usually not the faucet itself, a feature that dramatically reduces tooling costs.
Standardization has been especially beneficial to smaller faucet companies that do not own proprietary cartridge designs or technologies. A company like can design a new faucet around a standard ceramic cartridge with some assurance that it can be sourced from any number of suppliers, ensuring continuing production if a supplier fails, reduces quality, or raises prices.
Standardization, resulting in increased competition, is one of the primary reasons why the price of ceramic cartridge valves has dropped so dramatically over the past two decades. (Although, you as the retail buyer may not notice the decrease. But, that $55.00 replacement cartridge you just bought for your $1,200.00 designer faucet probably cost the faucet company about $17.50, down from $35.00 ten years ago.)
There are a lot of ceramic manufacturers. China alone boasts well over 200 technical ceramics companies. Most of these, however, manufacture for China's domestic market. Europe has another fifty or so. The U.S. and Canada have dozens of ceramics manufacturers including some of the best in the world, but very few make faucet cartridges. Most specialize in more high-tech products such as ballistic armor.
For years the general consensus in the faucet industry has been that the best ceramic disc valves are made in Germany and Italy. That may be slowly changing, however. The Asian ceramics industry, helped along by generous government subsidies and low-interest loans, has improved by leaps and bounds over the past two decades, and some Chinese and Taiwanese ceramics are beginning to rival the quality of those made in the West.
Flühs Drehtechnik, GmbH, a German firm located in Lüdenscheid, Germany since 1925, world-renown for its precision machining, is generally thought of as the manufacturer of the world's best single function stem cartridges. Flühs (sometimes spelled Fluehs for English speakers) valves are heavy-duty products with an established reputation for leak-free reliability.
A close runner-up to the Flühs primacy is Anton Tränkle, GmbH & Co. KG, also German, that makes superior single function ceramic cartridges out of brass for two-handle faucets.
There is no equivalent consensus about which company makes the best mixing cartridge for single-handle faucets.
Some of the better European cartridges are made in Italy which boasts a well-established ceramics industry. Studio Tecnico Sviluppo e Ricerche (STSR) S.r.l. and Hydroplast, S.r.L. are excellent Italian cartridge makers that supply dual-function ceramic cartridges to American faucet manufacturers.
One company that does seem to be pushing itself to the forefront, and has become the cartridge of choice of many upscale European faucets is Kerox Kft, a Hungarian manufacturer that makes only mixing cartridges. Unlike Flühs and Traenkle which started as machine shops making precision turned brass parts, Kerox started as a manufacturer of dental ceramics (which it still makes), and is well known for its high-quality ceramic discs which it sells to other cartridge manufacturers, including Delta for its Diamond Seal Technology® cartridges (see more below).
Sedal SA is another cartridge maker manufacturing good quality mixing cartridges. Headquartered in Barcelona, Spain, it manufactures in China. Sedal is considered to be somewhat below Kerox quality but still a reliable cartridge. It is popular with Chinese faucet manufacturers that make faucets for the North American market.
Cartridges from Wingbo Wanhai Cartridge Technology Co., Ltd. also a Chinese manufacturer, are starting to attract attention. Its cartridges are frequently included in Chinese-manufactured faucets destined for the European Union where the company sells under the Quore brand from offices in Spain and Italy.
Geann Industrial Co., Ltd. in business over 30 years, is a well-established Taiwanese manufacturer of ceramic disc cartridges of good to excellent quality. Ten years ago the company had a reputation for good quality reliable cartridges but nothing remarkable and nothing that made the cartridges stand out from a half dozen or so other Asian makers of good quality cartridges.
That has changed. Geann is gaining recognition as a cartridge on par with many of the best European products and is becoming the cartridge of choice for faucet companies that buy their faucets from Asian manufacturers. We are even starting to see Geann cartridges in some upscale faucet lines. The U.S. faucet manufacturer, for example, recently switched to Geann cartridges for its entire line of luxury faucets.
Kuching International Ltd., a ceramics manufacturer in Taiwan since 1988 has also made its mark in the industry with its KCG cartridges popular with Canadian faucet companies. The cartridges are considered roughly equivalent to Quore and Sedal.
Some of the ceramic casrtridges used in faucets are made by Maruwa Sdn. Bhd in Malaysia and by the Chinese company, Zhuhai Mingshi Ceramics Valve Co., Ltd.
Which Valve is Better?
Which valve is better? That's a question that can start a three-hour argument among the pros we know, and really cut into Miller time.
You probably cannot get most plumbers to install a traditional compression-type faucet in your home without an argument and possibly a bribe. But, that may depend on the valve. Most plumbers, especially the old-timers, like quarter-turn compression valves. Still, there are plumbers who would not use a compression valve if it were given a life-of-the-universe guarantee by the Almighty Herself.
But, homeowners in love with everything vintage won't use anything else. While compression and Fuller faucets need washer or plug replacement every few years, it's not very hard to do. If done regularly (so the valve seat is not damaged), the faucet valve will last nearly forever. And, even if the valve is damaged, it takes very little effort to hone it smooth again (although a special tool called a seat grinder, reseter, or seat hone, is required. Available at any plumbing store for about $10.00.).
We regularly see Sterling, faucets made in the early 20th century still in use and still functioning perfectly after nearly 100 years.
Moen cylinder and Delta ball valves last a long time. The rubber and plastic seals will eventually wear out after 5-10 years but replacing the seals is a job well within the capability of any homeowner who can handle a screwdriver without doing irreparable harm.
Ceramic disc cartridges can last a lifetime with no maintenance. They are replaceable if they finally fail and replacement is easy. The old cartridge is just thrown away, and a new one inserted. It's all done at the top of the faucet, not underneath the sink, and usually requires just an Allen wrench. The longest we have ever taken to replace one of these is about 10 minutes.
On the whole, with some exception, we give an edge to ceramic disc cartridge technology. It is the newest and in many ways the best technology, and it just keeps getting better. We think ceramic cartridges are just a little tougher and seem to give a little less trouble. But, we certainly will not discount Moen or Delta proprietary washerless valves. They have a track record second to none for longevity and reliability.
The super cartridges are changing the game, however. They are not yet widespread, mostly because they are patented by the companies that developed them. But, they are the products that deliver on the promise of an install-and-forget no-maintenance lifetime faucet. It's no surprise that the companies that have adopted super cartridge technology are ranked first in their respective categories in our review of Best Value Faucets. The super cartridges add enormous value to the companies' faucets at virtually no cost to the consumer.