Moen 3570 Valve passing water from cold supply to hot supply

[Jeff in Seattle]

Recently, I had to cut in a new branch for a bar sink off my 3/4" copper mains that run from one side of my basement to the other. In addition, I have shutoffs and drain plugs for both the hot and cold mains. Further, I have shutoffs for every branch to each room/appliance. Last time I had cut in a branch was long ago with no issue. 3 years ago, I remodeled my master bath and added a Moen 3570 Valve (w/balancing spool and stops). My previous shower valve (and my other shower valve circa 1991) did not have a balancing spool).

When I shut the hot main and opened the drain, the water (and pressure), kept coming. I finally isolated to the master bath branch, and then further isolated to the shower valve. Closing the cold stop on the shower valve, and the water and pressure ceased on the hot main. I deduced that the cold water, which was still on, was passing through the shower valve (I assume through the spooler cartridge) over to the hot feed - and then back down to the hot main via the master branch. This was easily remedied by shutting off the master bath feeds.

However, this was quite annoying to say the least and defeats the purpose of my main shutoffs. This leads me to my question: Can the hot or cold feed pass through/across the Moen 3570 shower valve to the other feed? If so, is this "normal"?!!? This is with the mixing valve in the off position of course and one feed on and pressurized and the other feed off and open to the air.

Thanks,
Jeff in Seattle

 

[Breplum]

I don't know the pathways through that valve, and I notice it is upside down, but, I have had many models of many shower valves that, in the OFF position, developed bypass failure. Amongst them that are common Kohler K304 series and older KWC shower valves. Replacing the innards always solved the problem.
First, pull the balancing spool and make sure the inner spindle is free. If it is, then the only other part inside is the cartridge. Just get a cheap plastic cartridge to try or call Moen for free lifetime warranty one. And on that call, ask them about it.

 

[Sponsor]

 

[Jeff in Seattle]

I don't know the pathways through that valve, and I notice it is upside down, but, I have had many models of many shower valves that, in the OFF position, developed bypass failure. Amongst them that are common Kohler K304 series and older KWC shower valves. Replacing the innards always solved the problem.
First, pull the balancing spool and make sure the inner spindle is free. If it is, then the only other part inside is the cartridge. Just get a cheap plastic cartridge to try or call Moen for free lifetime warranty one. And on that call, ask them about it.

Thanks Breplum, In this case the valve is for a shower only install with three diversions above. PMI, they state this should be the orientation with the bottom plugged. At any rate, I will pull the spooler and plunk in the new one. I was hoping for a definitive answer direct from Moen (no answer yet).

 

[hj]

It is the cartridge, not the spool

 

[GReynolds929]

Thanks Breplum, In this case the valve is for a shower only install with three diversions above. PMI, they state this should be the orientation with the bottom plugged. At any rate, I will pull the spooler and plunk in the new one. I was hoping for a definitive answer direct from Moen (no answer yet).

That valve is upside down. The installation instructions for the MoenTrol valve state to cap the tub outlet not turn the valve upside down and cap the shower outlet. Was it the transfer valve instructions you were referring to?