I have a new moen moentrol shower kit (rothbury trim T4211BN + 3330) - overhead rain shower hear and hand-held unit. There is a main on/off/temp control valve and a smaller valve that controls where thewater comes out (showerhead/ hand-held both). It works great, but it has randomly turned on, for no apparent reason - not full blast - I'd say 10-20%. Only way to stop is turn on, then off. It has happened about 4-5 times, but not for 2 weeks now. I called Moen and they said the only thing they could think of was low water pressure as the rubber seal/grommets require 40psi or they could leak. My water company says it never drop below 50-60psi in my area. They said that the pressure reducing valve could be failing - but I discovered that I do not have one in my house although it is required by code. Moen sent me 2 new valves but I have not swapped them yet. They very much doubt it is the valves. Any thoughts?

Hi Rpdcqd:

First thing I would recommend is that you test the pressure at your house using an outside faucet gauge... see image. The gauges are available at all home supply stores nowadays. Install the gauge and then open your outside faucet to see what the pressure reads. Then open an inside faucet and take another pressure reading outside. Let me know the results... OK?

I have included a picture of a pressure reducing valve just in case you run across something questionable... ;)

MARK

Thanks! I did as you suggest - I got a steady 60PSI from the outside hosebib - I then opened an inside faucet and the pressure slowly dropped to about 55psi and then slowly went back up to almost 60psi.

Hard for Moen to argue with that... huh?

Swap out the cartridge(s) Moen sent you. Be sure to purge the line of any sediments before reinstalling the new cartridge(s). Use a little plumber's silicone GREASE to grease the oring(s)... hopefully all you'll need to do here.

Let us know how you make out... O.K?

MARK

Thanks! I am a novice at plumbing - what did the above PSI tell you about the situation? Assume that it rules out water pressure and that the valves are defective? Thanks so much for your help!

It tells me that you are well above the 40 PSI Moen was concerned about, even when you are using fixtures, and therefore the valve and the cartridge must be the issue!

Keep me posted.

MARK