The Ceramic Disc Cartridge Valve

The America Standard response to the patented Moen and Delta washerless valves was to go its rivals one better and invent the modern ceramic disc cartridge.

The old, pre-breakup, America Standard was a pioneer as far back as the 1880s in the use of ceramics to make bathroom fixtures, so it seems entirely natural that it should put its industrial ceramics expertise to good use by creating a valve oem waterfall shower that used nearly indestructible ceramics rather than rubber to control water flow. But, evidently, the process was not as straightforward as all that.

Compression vs. Ceramic Stem Cartridges

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The ceramic stem cartridge (left) is designed to replace the traditional compression cartridge in two handle faucets. Water flow in the ceramic cartridge is controlled by the nearly indestructible ceramic discs. Water flow in the compression cartridge is controlled by the rubber or silicon compression washer, which tends to wear out fairly quickly. The blue silicone seal or seat on the ceramic cartridge indicates that it a cold side cartridge. Hot side cartridges usually have red seals. The two are not interchangeable.

Anatomy of a Ceramic Stem Cartridge

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Anatomy of a single function stem cartridge. This is a hot side cartridge from Tränkle for a two-handle fau­cet.

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 world of faucet valves and at risk of corrosion. They decided to replace the metal discs with a technical ceramic made of aluminum oxide — still the standard for ceramic discs today. After much experimentation and development, the company received patent number US 3810602 A for a "ceramic disc faucet" dating from 1972. It was a major breakthrough.

The American Standard ceramic disc valve used a pair of ceramic discs that rest against each other to control water flow. The discs are polished to near-perfect flatness. The space between the closed discs is smaller than a single molecule of water, which is why water cannot flow between them when they are closed. The technology eliminated wear on rubber rings and seals and vastly extended the service life of the valve.

Ceramic discs are very hard — harder than most 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 washers in compression faucets which can soften.

An ordinary run-of-the-mill ceramic disc valve easily lasts 5-10 years, and some super valves using diamond-like-carbon coatings are estimated to have a service life of nearly 550 years. The discs are housed in a removable cartridge which makes it simple to replace. Just pop out the worn cartridge and insert a new one.

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. But, over time the lubricant can be scrubbed away by the friction of water passing between the discs, china motion activated faucet which makes the faucet stiffer to operate.

Autopsy of a Failed Plastic Cartridge

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This cartridge failed when the retaining flange that positions the silicon seal deformed, permitting the seal to move out of its track.
The probable cause was a defect in the chemistry of the plastic.
The failure illustrates how a small error in the plastic formula can have big consequences in the finished product.

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, the abrasive effect of water and minerals in the water will ultimately wear it away. It may take longer, 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 is enough to not only improve the disc's hardness but create a very "slippery" surface that slides freely without the need for lubricant.

Types of Ceramic Cartridge Valves

Ceramic cartridge valves mimic the valve technologies

The single-function or stem cartridge, sometimes call the headworks, is used with two-handle faucets. It exactly duplicates the action of the older compression valve.Single-Function Stem Cartridge (or Headworks)

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 hotter. Decreasing the volume of hot water or increasing cold water flow makes the mix cooler.

Dual-Function Mixer Cartridge

One easy way to tell a single function from a dual function mixing cartridge is the count the ports at the bottom of the faucet. A mixing cartridge has three, a cold inlet, a hot inlet, and an outlet. A single function stem cartridge has two, an inlet and an outlet.

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.

A housing made of brass, aluminum, or stainless steel holds up very well. These metals are, however, relatively expensive, china motion sensor bathroom faucet suppliers so it did not take long for cartridge makers to start experimenting with less costly materials: primarily plastics.The movable parts of the cartridge – the stem and discs – are the most susceptible to wear and damage. These need to be strong. The housing does not need to be particularly durable. 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 applied when the faucet is operated (called "torque" in engineering circles). Enough torque applied to a jammed cartridge can twist a plastic stem completely off.

Plastics used in ceramic valves, primarily polyvinyl chloride (PVC), polyoxy­methyl­ene (POM), and nylon, 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.

Some of the 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. But, most plastics used in ceramic cartridges are not this durable.In the example shown in the sidebar