One of the most common product failures that WERC analyzes involves the failure of the inner Santoprene™ tubing of water supply lines. Santoprene products are a family of proprietary polymer compounds. Santoprene is a versatile polymer with a wide variety of uses and applications, including residential plumbing products; such as water heater supply lines and faucet supply lines.
WERC has analyzed thousands of plumbing supply lines with failed inner Santoprene tubing and the cause of the failure has been consistent for all of the supply lines. The chemical mechanism responsible for the failures is called oxidative degradation. Simply put, when the chlorine and copper in the water supply react with the Santoprene material, it causes the tubing to degrade from the inside out, which eventually causes the supply line to leak.
The chlorine present in most residential water supplies will readily react with and degrade many polymer compounds, including Santoprene. This reaction is accelerated with higher water temperatures.
For example, water heater connectors display a progression of degradation. They first become brittle and stiff, with a white chalky appearance. Eventually, the interior of the tubing will soften and start to flake away with increasing severity, as illustrated in the series of images to the right. Over time, the degradation fully penetrates the tubing and water sprays through the outer braiding. This often results in a large uncontrolled discharge of water and thousands of dollars in damages.
Some failures of faucet supply lines are similar to the water heater connector failures. Other faucet supply line failures occur as a result of the slow liquefaction and extrusion of the tubing material through the external stainless steel cover. In other words, the tubing material oozes out of the braided outer cover as the tubing degrades. This is illustrated in the photograph below. Note the degraded black polymer material protruding through the stainless steel cover. This process is worsened when the tubing material is exposed to a heat source, such as high water temperatures. Eventually, the extruded material will rupture, resulting in the failure of the supply line.
Manufacturers can protect against these failures in a number of ways. One way is by adding chemical compounds called antioxidants to the polymers to protect against this chlorine-copper-Santoprene reaction. Numerous manufacturers who have used Santoprene in their products have failed to take the necessary precautions to guard against oxidative degradation of the Santoprene and the ultimate failure of their product.
For more information on plumbing supply line failures involving Santoprene and WERC’s Product Failure Analysis Program please contact our office.