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Moen Shower Valve Keeps Running

3049 Views 33 Replies 7 Participants Last post by  Pat the Rat
My sis-in-law asked me to look at her shower valve as it trickles constantly no matter how the handle is turned on or off. It won't give any more water when it's turned on and keeps the same rate turned off so she had the main valve on the manifold turned off. I figured it was the valve cartridge so I got that out and took it to the hardware store and bought a new one, same model. But when I put it all back together it did exactly the same thing as the old cartridge did. It did not control the water rate at all and it constantly trickled out a steady stream of water. So I packed up the new cartridge and took it back for now (it was $45). What could be wrong with this valve? You'd think if it was the valve cartridge a new one would fix it. I did it exactly like several videos showed too. I'm kind of buffaloed as to how it can keep running like that.
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Fill us in on the type of valve. Is it a single handle, or two handles. Maybe posting a picture of it may help.
It's a single handle. Not exactly sure what the model is, but it was just like a few videos I've seen like this one:
i was thinking of testing it by removing the valve cartridge altogether and turning the water on. if I get a lot of water, then it would have to be the cartridge i would guess. If it's still a slow steady stream, then the problem if further down the line. but that would still not explain why the water would run despite the valve being replaced. i hardly think a new valve cartridge could exhibit the same symptoms as the old one. I'd hate to have to replace the whole valve body. the builder didn't provide an access panel on the other side of the wall. I'd have to cut the closet all out to get to it. any ideas welcome.
Hi...did you get the running water issue fixed yet? If not then try taking out the new cartridge and seeing if somehow the 2 parts separated, (the white from the blue as they can twist apart) If so then you should be able to put back together and install the cartridge again....don't forget to grease the seals. Good Luck
Still not fixed yet. I took the new one back out and it was intact. Nothing wrong with the way it went in and was lubed. I figured there was something else going on since the new valve cartridge did the same thing as the old one. the water would trickle out continuously at the same rate no matter what the handle setting was. Just doesn't seem logical to me. I put the old one back in and took the new one back to the h/w store thinking it was some other problem, but i have no idea what it could be. Why would a slow stream of water bypass a new cartridge and make its way to the faucet?
wondering if there may be a kink in the pex pipe somewhere? would a low flow allow it to bypass the valve and leak out the faucet?
Moen has a lifetime guarantee, so no need to buy a new cartridge. If you have a cartridge issue, they will send you one for free. Call them, describe their issue, and they may be able to help you.
Oh that's good to know. Thanks!
I have had that exact problem with the same valve at my cabin, and wish my memory was better so that I could be sure of how I corrected it. But I'm thinking that what I found was just a bit of lime buildup around one of the inlet ports that was allowing water to trickle in and push the cartridge out just enough for it to bypass. You don't want to use sandpaper, although maybe 1000 or up grit might do it without damaging anything, but I'm pretty sure I used a small piece of old wash cloth on a dowel to clean the bore.
thanks. that makes some sense. wondering if vinegar might be good to clean the bore out with too.
Yeah, vinegar on a swab might help, but better yet would be some CLR if you or she happens to have it.
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just an update. I had my sister-in-law call Moen and they are sending her a new valve cartridge. She said it was so simple and they were so nice. should get it in 5-7 days. I figured I might as well put a new cartridge in if I'm going to do it again. I'll try cleaning out the bore with a cloth dipped in white vinegar on a dowel then put the new cartridge in. hopefully that will solve the problem. otherwise I have no idea what to do.
My sis-in-law got the new cartridge from Moen and I installed it as per instructions but unfortunately it's still doing the exact same thing. It runs at this rate in the photo no matter what the handle is set to (on off or anything in between)
I looked int the bore when I replaced it and there was nothing obvious like a calcium buildup in the valve body. I still tried cleaning it a bit with a scrubby pad and some white vinegar but it didn't help. There seems to be good water throughput if the cartridge isn't in there as I just ran the water briefly with no cartridge in. so no blockage in the supply lines.

I called Moen support and they were very nice but had no ideas what would be causing it. All they could do was send her a whole new valve body to replace the old one with. No charge. I'd still rather figure out a fix for it if possible, because the builder did not leave an access panel to get to the back of the tub fixture and I'll have to cut a hole in the closet on the other side of the wall to get to it.

It's also connected with Pex fittings which I've never used before. Not sure what i will have to do to rehook up the supply lines to the new valve body.

Any ideas would be greatly appreciated!
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At least you have a closet to get at the valve.

If you have to cut a hole, just put an access panel in. Will make your life easier in the future.

Get the panel before you cut the hole.
yeah i will definitely install a permanent access door. i have along drill bit that I can drill beside the valve thru the closet wall to mark where it is, then i'll find were the nearest studs are to mount the panel.

Was looking on the Moen site and they suggest cleaning the bore out with a toothbrush then turning the water on to blow out anything in the lines for a minute. will have to close off the hole so it doesn't spray down and run thru the floor. she has a newly finished basement and i'd hate to ruin the ceiling panels down there with a water leak. maybe duct tape around the opening would do it. hope that works. i really don't want to replace the whole valve body.
It would be a good idea to flush after you clean. I had thought you had already done that.

Based on the way you are set up, will definitely want to put a pipe that turns down so water does not go behind the wall or shoot straight out.

A piece of pvc with a 45 degree elbow would work.

Tooth brush, bottle brush, gun cleaning brush, anything will work for cleaning.

Also, using CLR is well worth the few dollars it cost.
yeah maybe i'll pick up a bottle of CLR. I'm sure i'll use it again in the future. thanks.
Unless the shower valve body itself is damaged or pitted somehow they usually last for ever. As you say, everything looks smooth and shining inside. So it's hard to believe it would be the valve body. I have seen valve seats and springs needing replacement.

I agree, keep trying as suggested, with the flushing, and make sure cartridge is properly seated and lubed. Hope you get it fixed soon pat.
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You may also want to recheck the retaining clip. Pic is a little fuzzy, but it does not look seated all of the way.
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