Our water pressure was very low today in our shower. We have a three handle faucet fixture from approximately 1982. I did some research and it sounded like the diverter needed to be replaced. When I removed it, the plastic washer was almost completely disintegrated. I found a replacement at Home Depot (a Danco 9H-3D for a Price Pfister faucet) and installed it, and it looked like everything was fine. Shower water pressure was returned to normal. I noticed that the plastic O-ring from the new diverter had fallen off before I installed it, so I removed the diverter once more and put the O-ring back on. This time, though, the water pressure was back to the weak amount that I had before. I have not been able to recreate that one instant of good water pressure. I've tried every configuration: new valve, old valve, with and without the O-ring. I've even tried the old valve with the new plastic washer. The water all seems to be going up to the showerhead -- no water is coming out of the tub spigot when the shower is running. However, the amount of water coming out of the shower is nowhere near what comes out of the tub. Any suggestions? I read that using silicone grease on the washers can help give a better seal -- do they make that much of a difference? I can't figure out why the water pressure would change so abruptly.