Good call on the valve seat—I’ve seen that happen a bunch of times. If you’re gonna check it, here’s what I usually do: shut off the water, pull out the stem assembly, and shine a flashlight down there. Even tiny rough spots can chew through washers fast. If it looks rough, you can smooth it out with a valve seat grinder (they’re cheap at hardware stores). If it’s really bad, just replace the seat altogether—usually saves headaches down the road. Also, double-check your pressure regulator...high pressure can sneak up on you and cause leaks everywhere.
Valve seat issues are definitely sneaky little problems—good advice on checking the pressure regulator too. I had a similar issue last summer with my downstairs bathroom sink. Kept swapping washers every month or two, thinking that was the fix. Finally, took a closer look at the valve seat and sure enough, it had some tiny pits and rough edges. Funny thing is, I never even thought about pressure until a plumber buddy came over and casually mentioned it.
Turns out our pressure regulator was shot, and we were running way higher than recommended. No wonder I kept blowing through washers like crazy. Once I replaced the regulator and smoothed out the valve seat with one of those cheap grinding tools, haven't had to mess with it since. It's been almost a year now—knock on wood.
One thing I'd add: if you do end up replacing the valve seat altogether, make sure you get the right size and thread type. I learned the hard way that they're not exactly universal, even though they look pretty similar. Took me two trips back to the hardware store before I got it right. 😅
Anyway, good luck with your sink. Plumbing can be a pain sometimes, but it's always satisfying when you finally nail down the issue.
