For the past year, we've been experiencing periods when the bathroom shower and kitchen sink faucets dip in water pressure for weeks or months. Other faucets (bathroom sinks, laundry sink) work just fine. Then, for no reason, all the pressure is the same for awhile. I called the water utility and they came and checked the pressure at the ourside faucet and said it is fine. Is it possible that something is wrong with the valves in these faucets?

Would this be the hot, cold or both that have low pressure?
Did the water company give you the pressure that enters your home? If not call and ask what the PSI is out in the city main. Do you have a PRV (Pressure Regulating Valve) installed on your water service? Do you know what the water pressure is inside your house? Let me hear back from you. Regards, Tom

Both hot and cold are low; shower and kitchen have moen faucets with a one handle pull on or lift handle. We do have a pressure valve installed under the house because the utility company said the overall pressure for this area is too high. But 3 bathroom basin faucets and a utility faucet have great pressure. It's just the shower and kitchen sink. Weird.

That puts the problem in the branch that feeds the shower and kitchen. Are they close together or far apart? I'm trying to find out if you have one problem or two. In other words could one branch be supplying both fixtures? If not, (and I 'll bet they're not) then I would shut the water off to one of the valves and open it up. Check the inlet ports on the cartridge and then turn the water back on for a few seconds to flush out the supplies and open valve body. You should have a full stream coming out of the open valve. If not then tell me about it. If you need instructions on how to open up your Moen valve click on back. Regards, Tom