In a condominium constructed about 12-15 years ago in Henderson, NV, I discovered 6 out of 8 under-sink water shut-off valves to have badly corroded valve stems, if that term can be legitimately applied to plastic. The "corrosion" was so bad that one valve had failed causing a flood. Since 75% of 8 identical valves exhibited very bad signs of this "corrosion", it appears to be related to a chemical attack on the plastic caused by the water and possibly other nearby materials in the valve. The valve bodies were brass. The valve stems that were badly attacked were of a gray plastic. The only identification on the valves were the words "BOB" and "USA" molded into the clear plastic valve handles. What does this problem stem from and who made these valves? I have attached a photo of the worst example that failed.

The name or company symbol in on the handle. There is now warranty or liability on a 12/15 year old valve. Just go to Home depot/lowes and get new ones. Replace them all.

A strange, cheap looking thing. That damaged stem looks to me more like heat than chemical damage. If it doesn't mean adding too many extra fittings, I would put in ball valves. Much easier to work with, less likely to leak, and when shut off, stop all the water from flowing.

((I wanted to know what caused the problem. No valve of this type should expire so quickly!)

No one here will be able to tell you exactly what happened to the valve. That is why I said to look at the top of the valve handle to see if the manufactures name was there. That way you could call them and lodge a complaint.

A valve should never go bad but they are replaced all the time. I know of no reason a plastic valve should look like that unless someone was soldering a pipe or something above the valve and the hot solder dripped and melted it.

The whole thing is really strange. Was there once a nut on the threads where the valve stem comes out? Will the valve stem and internals screw right out? Even boiling water would hardly damage most plastics that would be used in such an application. Solder was a good suggestion, but I find it unlikely solder would have dripped on all of them. Have you compared yours to others in the condo?