Fun plumbing problem this morning: ~8 months ago we had new supply lines installed so we could add a utility sink. They installed shutoff valves for the new hot/cold lines in the spot where they branched off of the source (“isolation valves”). About 2 months ago, one of the shutoffs was leaking, and when the plumber came out to fix it (under warranty) he said he’d never seen anything like it in 30 years of plumbing – the shutoff valve itself had split open right in the middle of the metal casting (on the housing).

He fixed it, no charge, and left. Now the replacement is leaking again, and it looks like the same exact problem. I’m wondering if there’s something in the way it was installed or the way it’s being used that might cause it, any thoughts?

Getting a picture of the valve is difficult without removing it, but what I can tell you is:

• it's a ball valve with a handle
• plumbing is PEX w/whatever crimped/clamped connections that entails, no soldering AFAIK
• valve is on a hot water line in the basement
• despite cold temperatures it never gets below 48F in that room, it's right above the hot water heater, so I think we can rule out ice expansion

They're sending someone out tomorrow who I assume will fix it the same way using a brand new replacement part at no charge as before, so what I'm really trying to figure out now is whether there's something in the home causing the problem, so I can prevent it in the future, or whether this really is a bizarre case of the same kind of part failing twice in a very uncommon failure mode.