How to fix a leak from these shower fittings?

[David001]

We have a leak from either a shower mixer-unit or from the pipe which supplies the hose to the shower-head.

The shower (in an upstairs cubicle) hasn't been used for three years. 

 

We know we don't have a long-standing or a continual leak because a stain has only just appeared on the ceiling of the room beneath the shower cubicle.

If the drain-tray in the floor of the cubicle is not filled with a cup of water every six months or so a foul smell comes up from a soil pipe.

There was a nasty smell a few days ago, so the shower was turned on for just 30 seconds to fill the drain-tray.

The next day we noticed a water-stain had appeared on the ceiling of the room beneath.

The stain is directly beneath the wall on which the mixer-unit and hose-pipe are attached.

 

What's the easiest way to find out whether it's the mixer-unit or the hose connection which is leaking?

The wall behind the mixer-unit & hose connection is accessible, but can the leak only be fixed by cutting into the surface of that wall and examining the mixer-unit and hose-connection from the rear?

 

The photo shows the type of mixer-unit and hose-connection.

 

Thank you for your help.

 

[Bonner]

As it’s not leaking continuously, the problem is downstream from the mixer, from the outlet of the valve to the hose. Can you take the mixer cover plate off to see any leaks? Mine is turn and lock fitting. What about the hose outlet, have you tried taking that off?

[Nickfromwales]

Hi. Are you an avid DIY’er or not? The bottom outlet has the hose connected to it. Remove that first by undoing the nut. 
 

Then get a plumbing spanner/ grips and carefully undo the chrome elbow by turning it out anticlockwise.  
 

Remove the chrome disc. 
 

Now install a 1/2” male BSP plug with PTFE tape applied to the threads. Link

 

Turn the shower to the fully on position and report what happens next. If there’s no leak then the part you removed had not been sufficiently PTFE’d when installed and it was this that was leaking. 

 

If you have a leak with the blank plug in place then you have a leak on the connection from the shower valve on the output to the outlet you just tested. This means that tiles need to come off. 

[David001]

  On 20/03/2025 at 18:30, Bonner said:

As it’s not leaking continuously, the problem is downstream from the mixer, from the outlet of the valve to the hose. Can you take the mixer cover plate off to see any leaks? Mine is turn and lock fitting. What about the hose outlet, have you tried taking that off?

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@Bonner, so far with regard to the mixer-unit I have managed to move its large outer ring or plate a little in the anti-clockwise direction, but that didn't cause the plate to come away, so I am not sure what I should do next? 

How far should it turn anti-clockwise before it comes away?  (Roughly how many centimetres?) 

And once the plate is moved sufficiently anti-clockwise, does it then need some kind of encouragement or special action to make it come away?

 

Regarding the ring around the hose-fitting, I haven't yet been able to make it move.  I think I may need to use a fine clamp, so as to get a purchase on the outer edge of the ring.  What would you suggest?

[David001]

@Bonner and @Nickfromwales

 

Well, to my surprise, I have managed to remove the circular plate around the mixer-unit and the small circular plate around the hose-fitting! 

 

In both cases the interior of the wall is completely dry, with no sign of having been wet in the past.

 

I suppose this means that the leak must be from a pipe connection inside the wall cavity?

 

If so, does that mean that in the adjacent room a rectangle of plaster-board will have to be cut from the wall in the area behind the mixer-unit and the hose-fitting?

 

At least I may be able to guide a plumber as to where to do the repair.

 

@Nickfromwales, are you a plumber by any chance?  (I'm halfway between Llandrindod and Knighton.) 

 

 

Mixer-unit hole:

 

Hose-fitting hole:

 

[Bonner]

Well done for getting those off! It certainly points towards the connecting pipe unless there is a leak from the waste pipe (water can track across the ceiling and only appear at joints). Otherwise you will probably need to cut out the wall to find out what’s going on. Note I am only an amateur DIYer, suggest you wait for @Nickfromwales professional advice before going any further.

[Nickfromwales]

I’d get a bore scope camera and have a look inside the wall before cutting anything tbh. 
 

Most electricians carry these so maybe you can pull a favour and borrow one?

 

Just elongate the hole around the bottom of the shower valve cut out and the tiny camera head (with led light) will reach in there to see what’s actually leaking. 

[David001]

@Nickfromwales, thank you.

 

With your advice in mind, I've looked beneath the barrel of the mixer unit.  Below is a photo of the situation there.  The gap between the white ceramic tile and the barrel is just under a centimetre. 

 

I actually have a tiny camera (with LED light) on the end of a 2 metre "snake".  The camera at the end of the "snake" is just under a centimetre in diameter.  While I might be able to force the head through the gap it wouldn't be able to turn to peer around in the space.  It could only look straight ahead.

 

As the photo shows, there is a "wall" of pink plaster under the barrel.  And it's dry, with no sign of having been damp.  Would it be of any worth if I used a screwdriver & hammer to chisel it away so as to peer in further?  Would removal of the pink plaster destabilise the position of the barrel to cause problems in the future?

 

Thanks.

 

[Nickfromwales]

Nope. Just chip away the bare minimum and scope away 👍. Ideally you’d be looking to see the hot and cold inlets at best, or at the worst just a bit more info than guessing and cutting walks.

 

I have a 2m camera too, and the end can be formed into a tight curve so you can get it to look around corners so to speak.