Plumbers, advice please?

I think you are right. Just turn it enough that the water shuts off. If you really have to shut it off by turning really hard the seat that the washer pushes down against might be bad and wearing out the washer faster than normal. Just use the force neccessary to turn the water off.

O-rings and faucet washers are two different items in a faucet. If you over-tighten a faucet handle it will damage the faucet washer, causing the water to leak from the spout. If you have to exert much force to close the tap, that usually means the seating surface isdamaged, and new seats should be installed. Real plumbers ddon'tgrind seats, they use a seat wrench to replace them. If an o-ring is bad, the leak will be around the handle. Tightening has nothing to do with its wear. If your faucet is leaking by the handles, the o-ring needs to be replaced.

If it somewhat is percentpipe (plastic) then you definately'll would desire to decrease the pipes mandatory to take them out as on the factor of the joint as achievable. Re-sand the ends or the place you opt for the hot pipe to bypass with a hundred and fifty grit paper then sparkling and re-glue, put in new piece.

You can run a seat reamer on the surface of the seat to smooth it and remove any damage, you may also have the wrong washer in it. They come in many shapes from flat to tapered.

you should just seat the valve firmly if you have continual problems the valve seat is damaged and needs to be repaired bot o rings are only found on cartridge valve bodies which you do not over presser or you damage the cartridge Assembly and you need to rep lace the whole cartridge

Turning it really tight is always bad for it.

bad seat, i concur. tools & seats are available at all the major hardware chains, and it's pretty cheap, fast, & easy to do.