How To Look At A House
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What is a galvanized nipple?
Monday, June 25, 2018
A galvanized nipple is often used in water supply piping as the last, short section of pipe that penetrates the wall for attachment of a shut-off valve for a plumbing fixture. It has male threads at both ends. The photo above shows a galvanized nipple for water supply under a bathroom sink that has been recently replaced, but the wall has not been repaired, and you can see the copper piping it is connected to inside the wall.
One of the problems with galvanized nipples as they age is that the galvanized steel tends to develop a festering kind of rust called “galvanic corrosion,” which is an electrolytic reaction when you combine steel with copper and water. See our blog post What problems are caused by connecting copper pipe/tubing directly to galvanized steel pipe? to learn more about it.
This can result in early failure of the nipple, and a common place where we find it is at hose faucets like the one shown below. The corrosion has started a steady, slow leak in the wall, with a rusty drip stain as evidence.
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