Shower leaking behind wall
March 9, 2019 12:02 PM   Subscribe

This 28-year-old Grohe shower control is leaking behind the wall. This was discovered by water dripping downstairs when a shower was being taken (there is no dripping when only a bath is taken, and the caulk is in good shape). I'm pretty sure the issue is the diverter valve (at the top), as the week before the dripping was noticed, it was squirting water when taking a shower.

The squirting stopped after a few days, but it was replaced with just a slow leak from the diverter (which it has always done in the 8 years we've lived in this house). Then we noticed the dripping downstairs. It was not a slow drip, water was coming out beneath moulding a foot beneath the ceiling. There was enough water leaking that it triggered a GFCI outlet to click on an off for about a minute until the shower was turned off.

Of course, we stopped using the shower immediately.

I have not opened up the shower control yet, but I presume the diverter is the cause of leak. However, a few days later (after ordering a replacement valve) I noticed that the valve was loose, and I could screw it clockwise until it stopped turning (so, maybe I didn't really need to order a new valve). I'm waiting until the replacement part arrives before I open it up to confirm that was the cause of the problem.

So far, there's no visible water damage, but I want to prevent this from happening again. Since I'll have a new valve, I will replace the old one with it. But:

1) Should I use something like Loctite Threadlocker when reinstalling?

2) Could I use plumber's putty (which doesn't harden) to create some sort of shield that would catch any leaking water and redirect it so it runs out of the bottom of the cover plate into the bathtub?

3) I have no idea how long water was leaking and how much damage the water has caused. However, there's no visible damage to any walls. Once the leak is fixed, is there anything I should be doing to minimize the existing (and non-visible) damage?

(Here's the manual for the shower)
posted by ShooBoo to Home & Garden (3 answers total) 1 user marked this as a favorite
Best answer: I’m an enthusiastic amateur plumber.

Don’t use Loctite. It’s like krazy glue for your fittings and you’re going to want to be able to replace this valve at some point. There are different types of screw fittings. I don’t know what type you will have. NPT is designed to be used with Teflon tape to create a seal. Nptf does not take tape. The manual will likely tell you what to use. It will not be loctite!

Plumber’s putty is not going to stop a leak. It’s more for making a seal on a drain trap than attaching two fittings.

It’s up to you if you want to open the wall. Unless it was a huge leak and the drywall / green board was saturated, I’d just let it dry out and leave it be.
posted by Admiral Haddock at 12:18 PM on March 9, 2019 [2 favorites]

Best answer: Have you followed the maintenance instructions in the manual, i.e. removed, checked and possibly replaced the cartridge? Have you ever? After 28 years both looseness and leaking could be caused by disintegrating rubber seals or similar degradation.

I don’t know what part you were referring to when you said you ordered a new valve. This whole assembly is a valve, and (no offense intended) it doesn’t sound like you’re quite prepared to replace the entire unit. That’s where the NPT, NPTF, etc issues that Admiral Haddock mentioned could come into play. Hopefully you just ordered a new cartridge and maybe some diverter parts. Whatever they are, AH is absolutely right that loctite is not your friend here. Unless you’re replacing the entire valve body, Teflon tape isn’t appropriate either. Focus on replacing what’s broken (probably the cartridge) in the conventional way rather than jury-rigging some novel patch.
posted by jon1270 at 3:38 AM on March 10, 2019

Response by poster: I ordered a new cap assembly, cartridge and diverter. However, I first had to remove the existing cap assembly and cover and run the shower to see why it was leaking. When the current diverter was screwed in completely there was no leak. Which meant that I didn't really need to order any spare parts. Given that things were working and not leaking, I decided it was best to not replace the cartridge or diverter ("don't fix what isn't broken"). I did use the new cap assembly, though, so not all replacement parts went unused.
posted by ShooBoo at 11:19 AM on March 11, 2019

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