Machine Design

Scanning for Ideas: Faucet Fights Leaks and Drips

The Diamond Seal technology found in several faucets from the Delta Faucet Co., Indianapolis ( is said to eliminate leaks, simplify installation, meet California regulations on lead content, and last 5 million cycles or about 100 years of average use.

Key to the technology are two discs, one ceramic and the other encrusted with small bits of diamond.

Many faucets use two ceramic discs sliding against each other to control flow and determine the mixture ratio of hot-to-cold water. But the two discs need a lubricant to let them slide easily. When the lubricant eventually washes away, the two discs can stick together (stiction), making it hard to operate the faucet. And in areas with hard water, the calcium tends to bind with the alumina in the ceramic discs. These deposits degrade performance and can cause drips.

In the Delta faucet, the diamond-coated disc slides relatively smoothly over the ceramic disc, thanks to a low coefficient of friction. This means no lubrication is needed. And the diamond-coated disc acts as an abrasive against the other disc, keeping it clean and free of deposits.

The Faucet also has no dynamic seals, so they cannot wear out. Instead, static-silicone seals remain pliable without drying out. They also have a low propensity for compression set (less than 2%, compared to 10 to 15% for conventional rubber seals). This means that when compression is released, the seals return to their original shape and size. The faucets have steel stems or handles, which are considerably stronger than the plastic handles used on some faucets. The handle also has an adjustable limit stop. It lets users limit how much hot water is mixed with cold water.

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