Possible leak behind wall in wet room All aspects of plumbing questions and answers, help, tips and information

[rm_london]

I've got a wet room. Some time after I've showered I've noticed a leak appears at the foot of the wall next to the wall where the shower bar valve is mounted. There's clearly a leak but I can't understand why it only appears after I've had the valve turned on. It ISN'T constant. If I don't use the shower then there's no leak. Maybe the shower bar valve has beeh fitted incorrectly so water leaks back into the walll when it is tuned on or maybe there's a leak that is behind the tiles meaning they'll all have to come off, costing thousands. Any opinions would be greatly appreciated.

[stoneyboy]

Hi rm_london
Assuming there are no gaps in the grouting the most likely issue is that the stubs that the valve screws onto have not been sealed to the wall. You will need to look behind any chrome cuffs that are fitted.
Regards S

[rm_london]

Hi stoneyboy, thanks very much for your reply. The shower bar valve is a Bristan Frenzy I believe. The wet room was fitted 2 years ago by Bath Store (went into Administration June 2019). I should have cancelled it when the "team" turned up to do it, they were, funnily enough, "a shower" themselves. But I didn't. I've had nightmares literally about having all the tiles removed. I have a plumber coming on Monday to replace the shower bar valve. The right-hand temperature control has seized solid apart from the other problems. I'm praying that the leak can be fixed without ripping it down. Thanks again.

[stoneyboy]

Hi rm_london
Since you do not get the leak until the shower is used water must be getting behind the tiles. If the stubs are sealed then water is getting through the grouting and a rake out re-grout will be the next step.
Regards S

[rm_london]

I can see what you mean. I've been very careful to avoid water getting onto the walls when Ive been showering since I discovered the leak. I sit on the floor, I've got bin liners taped to the walls. It's not a pretty sight. There's definitely not enough water getting onto the walls to penetrate them and then leak back out again.

I'm sure it's not happening that way. I might be wrong. I don't think it's a badly soldered joint behind the tiles because then I would see the leaking all the time and I do not. It occurs about 5 minutes after the shower has been used - base of the wall in 2 places - 1 drip every couple of seconds for about 10 minutes gradually reducing. It's as though water has tyrickled down and sought out these 2 small openings at the floor/wall junction where the mastic meets the grout. I think it must be the shower bar valve leaking back into the wall somehow when water flows through it. I am just praying that replacing the valve will solve the problem.

[stoneyboy]

Hi rm_london,
Thanks for the update please let us know what happens.
Regards S

[rm_london]

I had the shower bar valve replaced on the basis that the joints with the stubs might have been leaking back into the wall. It made no difference whatsoever. I am at a loss. The leak only appears a few minutes after the shower has been used. It's about 2m from the valve and at shower floor level.
The boiler is a Worcester Greenstar 24i Junior Combo Mark IV GC4. It might help if I could tell if the leak was coming from the hot pipe or the cold pipe. Anyone know if the pressure in the hot & cold pipes will be the same when the flow is on and the boiler is running? I'm wondering if the pressure in the hot pipe increases during use and a slow leak becomes faster and appears through the small hole in the junction between the grout and the mastic. Any suggestions gratefully received.

[stoneyboy]

Hi rm_london
The static pressure in the pipes (when you’re not using the shower) will be higher so a leak is unlikely. There is the remote possibility that when you use the shower the hot pipe gets hot and opens up a joint.
Can you try hanging a sheet of plastic over the area directly below the shower head and into the tray to eliminate water passing through the joints.
Regards S

[rm_london]

I've attached an image of the relative positions of the shower bar valve and the leaks. 1 leak is definite, the other is water that appears in the air gap directly beneath the shower screen. This has been sealed all around with silicone. I can't see how water gets into this long thin air gap. I can't see how water gets to the leak on the other side either. The floor was raised 6 inches to give space for the plumbing from the shower drain etc. This was all installed 2 years ago. I'm beginning to think that I'm standing on a lake which has accumulated under the raised floor. I think I may have to have the whole thing ripped out.

[stoneyboy]

Hi rm_london.
Underneath the tiled floor of the shower there should be a tanked shower tray. It looks like water is penetrating the floor tiles. The tanking should have been taken into the central drain but it is likely this has not been done.
A strip out will be financially painful so try using grout sealer first but it’s probably best to let it dry out for some time before you apply sealer.
Regards S

[rm_london]

Thanks for all your help. I had a consultation with a company that installs wet rooms. Their conclusion was that the grouting was degrading and had become permeable above the "leak". I was able to confirm this by running a hot shower, via the shower hose, straight down the nearby toilet. I let the water run for a long while. There was no leak. If I had a leak behind the tiles that was opening up when a joint was hot it would have leaked. It didn't. No water was getting on the walls or floor. There was no leak whatsoever. I've concluded that they are correct and I need to have a bit of re-grouting done.
The water in the air-gap under the shower screen was caused (in their view) by the screen being sealed with silicone along both sides so water could not escape or evaporate. They recommended having the screen resealed but along the shower side only so that any slight leakage under the screen could evaporate via the unsealed side.
I thought this all sounded quite convincing. They spent a good hour looking at the room. Thanks for all the helpful suggestions.

[stoneyboy]

Hi rmlondon.
Many thanks for keeping us up-to-date.
Since there will be water under the floor tiles it may be worth raking out the existing grout and then leaving the shower unused for a week to dry out.
Regards S