Diagnosing and fixing a leak in a first floor bathroom

[Nigel Watts]

There is a nasty damp stain on my drawing room ceiling immediately below the position of the drain of the shower in the bathroom on the floor above, which I have now banned anyone from using.

The bathroom floor has plywood screwed down over the original floorboards which in turn is covered in lino. There is no waterproof membrane as I understand is often used these days in wet rooms. The joint between the floor and the shower tray is sealed with silicone mastic. The shower tray sits directly on the original floorboards and the U bend extends into the void between the floor and the ceiling of the drawing room.

The source of the leak could be a plumbing defect or it could be water which has overflowed the shower tray and penetrated the seal. The shower outflow often gets a bit blocked, probably because there is insufficient fall between the U bend and where the pipe exists through the external wall, but I suspect the former.

Should I:

a. cut a hole in the drawing room ceiling and try to diagnose/mend the problem from below (the ceiling is original lath and plaster but not in great shape). I'm not too keen on this as more might come down than I anticipate.
b. cut a hole in the lino/plywood to access the U bend and then try to make good by patching in a new piece.
c. something else?

A solution to this problem will please my wife no end.

 

[Feltwell]

Luckily lath & plaster is quite tolerant of a short-term soaking, certainly compared to a plasterboard ceiling.

It's difficult to say without seeing it, but it sounds to me like the best option would be to take the shower tray out. I note you didn't list this as a set option, is there a particular reason why? Will it mean re-tiling?

Lifting the lino and chopping into the floor outside of the tray is an option, you could do it neatly and make good afterwards, but my concern is would it actually get you the access that you need not only to see what the problem is but also to fix it? You won't know until you're in there.

Taking the tray out and effectively re-installing the original job from scratch would to my mind be the most thorough way of doing it. If you have had a problem with the shower tray overflowing, surely whoever was using the shower at the time would have noticed that?

What's the seal between the top of the tray and the walls / enclosure like? That's another weak point that you may want to try re-doing before resorting to taking the tray out, if taking the tray out means major re-tiling work.

Cutting holes in the ceiling from below would be a very messy job and difficult to patch back again seamlessly. I'd avoid that unless you think the ceiling is really so bad that it needs replacing anyway. Even then, taking a ceiling down from below would be a horrendously mucky job.

 

[Nigel Watts]

Good tips - thanks

The shower tray is large and I can't see how it could easily be lifted without disconnecting the pipework first. The seals between the tray and walls had already failed and been fixed. My teenage son uses the shower and could easily have caused an overflow without noticing or telling me.

 

[Feltwell]

The joys of teenagers! I guess the easy way to test the overflow theory is simply run the shower on cold, full blast, for 20 minutes or so - does it ever put enough water in to the tray compared to the outflow for this to be likely?

It's possible it was originally installed so that the waste was positioned underneath the tray, then the tray put on top and the waste screwed into place from above with a bit of sealant - this makes it clearer:-

https://www.youtube.com/watch?v=AnVzhLM_cg8

So you may be able to separate the waste from the tray before lifting the tray out. Will be a tricky job though, and it will be likely to be well gummed up even if sealant wasn't used.

Or, and a way I've done it in a past house, was to install the waste on the tray, then lower the tray into position and connect the pipework from a little hatch cut just to one side, like this.

http://www.homebase.co.uk/en/static/how-to-fit-a-shower-cubicle

Tricky to tell what your installers did as if they did cut in an access presumably they then covered that with the ply.

I think whichever way you do this it's going to be an invasive job with plenty of making good afterwards. No easy way . After your previous wall/tray seal failures I'm presuming the original installers already weren't at the top of your Christmas card list.

Presumably you are going to have to disturb the lino anyway. If you can peel this back, then on reflection I think I'd start with the "cutting in an access to the waste through the floor just outside the tray" method - as if it doesn't work then it's not that hard to put it back. Various different ways to cut into the ply in-situ, but one of the easiest is with an oscillating multi-tool cutter - they are great for these kind of "plunging cuts", and have a thin kerf so the bit you cut out can usually go back in afterwards on new supports screwed to the sides of the joists & underside of neighbouring boards. These tools have become quite cheap over the last couple of years, plenty of copies out there so no need to spend a fortune on a Fein Multimaster now. Or just use a flooring saw with a curved end, but I've always hated using those! I've never liked drilling a hole through then using a jigsaw as some do, as you've no idea what you're cutting through - far too easy to cut through a pipe or cable - you've a lot more control with the oscillating tool to just barely cut through the bottom of the floorboard then stop!

 

[Penners]

I agree with everything that Feltwell says in his original post.

I assume that you have minutely examined the silicone sealant bead, to be absolutely certain that it hasn't split or parted company with the wall or the shower tray at some point? Sometimes, such faults can occur - particularly on suspended floors - and are only visible when the shower tray has the weight of a person on it. No matter how much the floor may have been reinforced, it's almost impossible completely to eliminate the risk of imperceptible flexing.

Have you also looked very carefully at the construction of the shower cabinet, to ensure that there isn't some corner of it where water can worm its way through a small gap? I have exactly this problem with a recently installed shower, and it took me weeks to identify the route of the infuriating leak.

However, assuming that the above possibilities have been eliminated, then it seems inevitable that a plumbing leak is to blame.

Having experienced a number of shower outflow leaks in my time, I absolutely agree that cutting into the floor outside the shower cabinet is unlikely to give you enough access and visibility to be able to fix the problem from that point (unless the shower's drain hole is very close to the point where you're able to lift the floor). You can of course try this route, but I have a nasty feeling that you will ultimately end up either (a) removing the shower tray (what hassle!) or (b) cutting a hole in the downstairs ceiling (ditto!).

Sorry to be pessimistic!

 

[Feltwell]

Having experienced a number of shower outflow leaks in my time, I absolutely agree that cutting into the floor outside the shower cabinet is unlikely to give you enough access and visibility to be able to fix the problem from that point (unless the shower's drain hole is very close to the point where you're able to lift the floor). You can of course try this route, but I have a nasty feeling that you will ultimately end up either (a) removing the shower tray (what hassle!) or (b) cutting a hole in the downstairs ceiling (ditto!).

Sorry to be pessimistic!

Realistic more than pessimistic I think! The only other advantage to the cutting into the floor outside the tray is you may be able to leave the waste attached to the tray, even if you end up taking the tray out. Providing, of course, that is not the source of the leak.

At my mother-in-laws house, she has a damp patch on a kitchen wall that may be caused by damp coming in from outside, but may be coming from the bathroom above. I've sorted the "outside" issues recently and am praying that does the job, as the bathroom has been in place since the 60's and previous experience tells me that all the plastic waste pipework in that house is old and brittle and doesn't like being disturbed. It could be a can of worms!

A nasty job to have to do Nigel, you have my sympathy.

 

[Penners]

At my mother-in-laws house, she has a damp patch on a kitchen wall that may be caused by damp coming in from outside

Feltwell has a point. You expressed some doubt as to whether the waste pipe from the trap has a proper fall on it, before it passes through the outside wall of the house. If, by any chance, it does not, and if the pipe hasn't been properly sealed outside where it emerges from the wall of the house, could there have been a leak of rainwater passing through the wall and running along the outside of the pipe under the shower?

A pretty unlikely scenario, I agree, but it might just be worth climbing a ladder and examining the pipe's egress point, before you start extensive surgery inside.

 

[Feltwell]

Indeed - got to be worth a check. Took me ages (and a lot of helpful suggestions from this 'ere forum) to finally work out that I had a central heating header tank that was overflowing ever so slightly when the heating had been on for a while, this was travelling down the overflow pipe, out through the wall of the house and then running back down the outside of the pipe, as it was sloping upwards as it left the wall. This series of tiny drips caused a huge damp patch to form over time. A lot of other factors, such as a roof abutting onto a wall, a leaky downpipe, and leaks in the plumbing above all looked more likely until they were gradually eliminated.

http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=10283&hilit=kitchen&start=15

 

[Nigel Watts]

The waste is very close to the front edge of the tray and when I laid the plywood I noticed that the builder had cut a little hatch in the floor in front of the tray. I remember thinking at the time that covering this may cause a problem in future (in general I hate the idea of plumbing built into structures which cannot readily be accessed without major demolition works, but modern aesthetics seems to demand it).

I am warming to the idea of trying to lift the tray not least because this could give me the opportunity of raising it a little thereby increasing the fall on the waste pipe. The tray was also not fitted correctly where it met the walls. The instructions clearly state that the tray should be set into the wall by about 10 to 15mm, but it was in fact butted to the wall with the result that water penetrated the gap as the floor flexed. I fixed this a while back using some proprietary pvc extrusions fixed in with silicone.

This is the shower type:

Thats's not 'er indoors, by the way; the picture is from the manufacturer's website.

 

[plasticpigeon]

I usually use the toilet but i have had a leak in my shower once or twice!!!

Seriously, one time it was leaking it turned out that water was getting round the plug hole insert between shower tray and the strainer/plughole thing. I took the strainer out and siliconed the bottom and put it back in. It would be a miracle if it was that simple but it might be a first thing to try.

 

[LadyArowana]

I usually use the toilet but i have had a leak in my shower once or twice!!!

Eeeeeeeeeew. Too. Much. Information.

Showers always seem to give rise to leaks, yet one more reason I dislike them so much. I know that when the time comes there will be a fight with His Lordship about the bathroom at the house. It is presently designed with a bath and a shower and one sink unit. If it was up to me then I would dispense with the shower and have a lovely double sink unit and a fireplace feature instead. Like Nigel's bathroom it is above a reception room and the possibility of leaks concerns me.

 

[Flyfisher]

There's a simple trick for a non-leaking shower . . . Upstands.

I've never known a shower tray with upstands to leak. 15 years with no problem at a previous house and 6 years for the one I built here. Forget about silicone stuff forming a reliable seal.

 

[Penners]

I agree, FF. Shower trays with built-in upstands are an excellent solution. In fact, I wonder why any other types of tray are made, nowadays.

The only downside to them is that they're almost impossible to retro-fit without tearing out at least the bottom course of tiling.

However, not all shower leaks are caused by poor tray-to-wall sealing - unfortunately!

 

[Flyfisher]

True, though retrofitting should be unnecessary if adequate access is also given to the waste piping. Unfortunately, a low profile trays often makes this impossible, making maintenance difficult without major disruption.

 

[Zebra]

I'd be tempted to think that the most readily sacrificed part would be the lino, and the plywood. If, as you say, you remember a hatch having been cut in the floorboards before the plywood was fitted, then surely this is the bit to get to, as this will be likely to allow access to the plumbing, at least to have a look and a feel to see if the waste is wet?

 

[Nigel Watts]

I have decided to cut a hole in the floor as a first step and I have ordered a Bosch oscillating multitool. Will post on progress.

 

[Penners]

Please do - it will be interesting and informative to know how you get on.

 

[Nigel Watts]

Following the excellent (as always) advice received here, I have started the process to diagnose and repair the leak. I first marked a rectangle in the lino and cut round it with a Stanley knife. The lino came up cleanly and in one piece with the help of a filling knife. The only damage was a small 1" tear which won't notice.

I then used my new Bosch oscillating tool to cut through the 8mm ply. What a wonderful piece of kit for this type of thing! I put a piece of masking tape on the blade to act asa depth indicator. The ply came up remarkably cleanly.

Finally I removed the pieces of floorboard adjacent to the u bend and outflow. On testing it was very clear there there is a major leak in this area. I have yet to disassemble the fitting to establish the exact cause.

Will keep posting as project progresses.

 

[Penners]

...the u bend and outflow. On testing it was very clear there there is a major leak in this area.

That's great news! That's possibly a strange thing to say, but water leaks can be the very devil to trace, so it's great to investigate and discover a very obvious cause.

If you want to be belt-and-braces about remaking a plastic push-fit or compression joint, I heartily recommend LS-X sealant. It comes in a smallish tube and is a bit like clear silicone. Just smear it around the mating surfaces and it makes an excellent seal. Spray a bit water on the surfaces first, to aid curing.

 

[Flyfisher]

I agree . . . on both points.

Finding the leak, especially when all pipework is boxed in, is a major milestone and like many of these things the actual repair should be fairly easy. I also wouldn't be without LS-X for such repairs. It may not strictly be necessary with clean pipework and good condition joints, but this is exactly the sort of situation where belt and braces will pay dividends and is certainly worth the cost of a tube of LS-X.

I wonder if there is any clue about why the joint has failed? Sometimes pipes can be 'forced' into certain positions before making the joint, which leaves a strain on them. As the joint is gently disturbed by temperature changes during use, any strain can cause pipework to move apart.