Since the valve stems don't have a brand name anywhere on them I am concerned I may get the wrong size or thread type. Are plumbing parts consistent all across the board? I just can't seem to get this drip to stop completely. I can slow it down, but the washer ends up getting wrecked in about 3 weeks or a month and here we go tightening it closed harder and harder and eventually replacing it (again). The valve seats look o.k., and it wouldn't cost much to replace, but again, if I get the wrong size or thread type and then screw up the female thread it would take lots of money to fix that. Any advice out there on how standard these items are as far as sizes/threads are concerned?

Old Toolmaker

Hi, RobDot

It's pretty hard to blind diagnose, but I've done this same routine several times. The problem is likely the seat, not the stem or washer. Although you should put a new washer in when you re-install a new seat. The reason it keeps leaking after a new washer is a very small groove cut across the face of the seat. This happens with water pressure leaking in the same spot over time. Sort of like erosion of rock by water.

First, can you get the old seat out ? If it screws out, CAREFULLY remove it. Most seats are right hand threads, so turn the removal tool counterclockwise. Some seats do not screw out, and are pressed in. More difficult to remove. Usually you have to tap the hole in the seat and use some type of pull hammer to get them out. Best left to a plumber unless you're pretty mechanical.

Take the old seat to some old time hardware store first. They have gauges to check the thread and give you a correct replacement seat. If they don't have it, take it to some larger plumbing supply house. There are usually one or more in any larger city. Chain stores may or may not have the correct seat, but for sure they won't have anyone capable of assisting you. Most of their stuff will be for more modern faucets.

Threaded seats re-install pretty easily. Pressed in seats are not too bad, just take care to keep them level when going back into the hole. A stepped wood dowell pin works pretty well, or there is a tool made for the purpose (plumbing supply house).

Tip: before re-installing the new seat, coat the DRY threads with an anti-seize compound or silicone grease...just a little....this will make removal much easier in the future.

If you can't remove the seat, a last ditch effort can be to purchase a seat re-cutting tool, also available at hardware stores. These are a little tricky to use, that's why do it last. Sometimes a seat has the groove just too darn deep to cut out, and replacement of the seat or faucet unit is the only option.

Good luck, and let me know how you come out.
Old Toolmaker