Problem and defective water shut off valves

In Home maintenance tips, Plumbing by Mark Goodman

valve body corrosionThe other day I was doing a home inspection for a buyer and ran across a situation which we are seeing more frequently. The issue I found was defective water shut off valves which were exhibiting valve body corrosion. These defective valves we are typically finding in homes built in the last 20 years. Most of the valves are indicative of import water stop valves and if you find one or two odds are that most of your valves may be effected.

How do you know if you have any defective water shut off valves?

Here’s how you can tell. While your doing your own water valve inspection visually check all of your water shut off valves for potential issues, if you can reach them feel them to make sure they are dry specifically around the valve stem (where the handle is). The specific one ones I am referring to are typical valves installed in your copper supply lines by permanently sweating the valve in place with solder. Your looking for valve body corrosion which is calcium buildup on the exterior of the valve that looks like a growth.

These growths form from a weep hole in the valve body (bad casting) allowing buildup of calcium that appears as a growth and over time can build up to look like cauliflower. In most cases the calcium seals the weep hole to stop the leek but will continue to grow. Problem is no one knows if or how long it will be before it will develop into a leek that could potentially cost you thousands of dollars in repairs and damages. Best thing to do is replace them. We will talk about the different types of valves later in the blog article. But first lets talk about other things to look for.

valve leaking at the valve stemWhen checking the remainder of the water shut off valves in your house or business look for corrosion around the stems, corrosion at the cap on the side of the valve or wet valves. Don’t forget to inspect the valves under your sinks and toilets Depending on the type corrosion or water around the valve stem it may just need a new washer, packing or the packing nut to be tightened. If your not sure how or what to do the best thing is to call a plumber. Whenever your repairing or replacing a water valve make sure you turn your main water supply valve off first.

You can replace valves with the solder sweat on type, push on (shark-bite) type or compression valves. If you don’t want to use the compression style and don’t know how to solder call a plumber.

water valve cut-away diagram


Types of valves

There are three main types of valves with a few other less common types. Valves should be marked for use with water, oil or air. Valves stamped with “WOG” can be used for for all three.

Globe or washered water shut off valve (also known as a stop or stop and waste valve) – are closed by screwing the stem down with a rubber washer against a seat in the middle of the valve.
Gate valve – to open or close the valve it moves a rectangular gate up or down in the waters path.
Ball valve – contain a finely machined stainless steel ball with a hole
Some styles available in full or quarter turn

A good illustration of the different valve types and how they work can be found at