The hot/cold mix of my shower began to malfunction a week ago. I can no longer get water hotter than warm. The main component of the valve is a 2-piece plastic part and one of the small rivets came out resulting a slight separation. This part has two ports with spring loaded washers that press against a stainless mixing "plate" which is turned by the handle. Access to replace the entire unit would require opening up a bigger hole in my one-piece tile wall. Is anyone familiar with this type of design, approx 12 yrs old, and can the unit be repaired without removing the valve body from the pipes? There is no access to replace the rivet. I may eventually try some sort of epoxy to close up the open seam but I'm concerned that I may plug up some critical orifices or who knows what.

Thanks,
Breighty

Take the entire cartridge to a plumbing repair supply house and replace the whole cartridge. What brand is it? Price pfister has a lifetime warranty as do others. Kissler.com

Thanks for the reply, Doug. From the little access I have to the unit, I can no see any manufacturer's name. The plastic valve which is deffective, is inside the cast housing and I assume is mechaically attached in a way I cannot access. Is it possible the plastic valve can simply be pulled out with a slight bit of effort?

My plan right now is to take a picture of the unit and go to a major plumbing supply house here in Louisville and purchase a similar unit to either replace the deffecitve components or call a plumber to install it. Unfortunately there is no single shut off valve for the shower so once I is taken apart, the house water cannot be turned on again until is fixed.

Thank again

Go to kissler.com, match the handle and likely you will match the faucet.

Thanks, again, Doug. I couldn't get very far with the Kissler web site but had great success at the plumbing supply house here in Louisville. The first one didn't have the correct parts but a catalog picture kinda' identified the valve as a Price Pfiester (?) and they sent me down the street. Oddly enough, the valve I needed was on the counter from another customer's return. The black plastic valve does pull out of the cast body and I was able to repair it by replacing the failed rivets with small machine screws. So far, all is well. I will keep the new valve ($28) anyway, just in case the old one fails and becomes obsolete. Subsequent owners of my house may be graterful some day. Thanks again, Doug, I appreciated your concern and input.
George