We have a leak - but where? Help! Any plumbers around?

[kingfisherblue33]

A couple of weeks ago dd was letting out the bath when we noticed a small puddle of water at the foot of the stairs. It was coming out from under the stairs - we have an alcove under the stairs.

At the same time, we also noticed some small bumps in our kitchen ceiling that followed the line of the joists across the ceiling. They looked like damp bumps - but I pushed one and it crumbled; no water.

So we got a plumber out. He took off the side of the bath and checked all pipes under the bath - there's no damp.

He says the cold mains pipe under the bath has a lot of condensation on it (it's very close to a hot pipe) but surely there's no way that condensation could cause that much of a puddle at the foot of the stairs??

Don't know where ot go from here. Next step is to remove the bath and the bathroom floor to check remainder of pipes, but this will be costly and inconvenient. There has only been a leak twice in the past 3 months, maybe, and the bath is used every day.

Our house was built in the 1980s. It's well ventilated and doesn't smell damp. But we'd like to get to the bottom of this...

Our bathrom is at the top of the stairs.

condensation on the pipe is due to dampness in the air. It may be that you have frequent leaks but they are small enough to be absorbed and dry out.

Looking under the floor will give more clues.

If the water appeared after a shower had been used, it may be running down the gap between bath and wall. if it appeared after splashing about in a well-filled bath, it might be coming from a leaky bath overflow.

I'd leave the bath panel off, with a torch handy, and look for signs of wet every time the bath is used.

In a 1980's house, the waste pipe from the bath probably runs under the floor and joins into the main soil pipe which probably runs vertically in a duct in the corner of the bathroom and the kitchen beneath. If it is leaking it is more likely to be at a joint, e.g. where the bath trap goes into it, or where it joins the SVP. It may also have joints for the shower and basin to connect into it. If there have been extensions and alterations since the house was built, they should be viewed with extra suspicion.

The ceiling marks suggest long-term leakage.

if you see signs of water on a ceiling, poke a hole through the plasterboard with a skewer. Next time there is a leak the water will drip out so you will immediately detect it, instead of soaking into the plaster. You can put a bucket underneath.

it is easy to fill and redecorate a skewer hole once the fault has been found and rectified.

Is there a shower above the bath? Spray water around the seal of bath and wall, with panel off check for seepage. Fill bath above overflow level and check. Allow full bath to empty and check ceilings. Repeat several times. Rodents have been known to gnaw through the top of waste pipes, this would only leak when pipe is full of water. Be patient!

Ooh, I hoped you would be around, John!

There’s not much room under the bath for the pipes, so not enough room for any dampness to go?

Will skewer the plaster and wait...

We had a new bathroom put in 10 years ago and we moved the loo and sink, so we have new plumbing. The plumber checked all the joints that he could see.

So would you have the bathroom floor and bath removed?

Thanks, John!

and plummy, too.

I like to get the floor up so you can see what's going on. When it's renewed, I'd go for 22mm WBP ply, which is water resistant (unlike chipboard, which is rubbish) screwed down so you can lift it and have a look if necessary.

If it was me I might leave the floor under the bath till last, depending on the joist direction you may be able to see under there before removing the bath. You might find and fix the fault before the bath comes out.

If it was supply pipe work, hot and cold, it would be a constant leak. One other thing is to make the WC overflow, it may just run into the pan but it just might be the cause. Do not think that the point of leakage through the ceiling is below the fault, water will travel a long way to find a weak spot! Fill and overflow the basin as well.

Thanks, Plummy! There is a shower in the bath. We have sprayed water all over the wall and sealant and checked under the bath, but there is no leak.

We have also filled bath to full then let out. We check every eve when dd lets out the bath too.

How do I make the loo overflow?!

Will try the basin too, but would enough water be going through it to make a leak?

Good idea to have floor removed and leave bath until last...

The kitchen is not directly below the bathroom. There is no obvious damage to the utility room ceiling, which is directly below the bathroom.

Could the leak be e.g. from pipes to/from the radiator in the spare room, which is directly above the kitchen??

An intermittent leak is rarely from a heating or supply pipe, usually from a waste or overflow.
First thing have you smelled the pool of 'water' that appears? Could it be from a dog, cat or errant husband sleepwalking after a night at the rugby club?
Next what type of heating/hot water system do you have. Do you have roof tanks or an unvented/ sealed system?
If you have a sealed heating system the pressure gauge would show a drop if anything on it were leaking.
Could the water be coming from a softener, washing machine or dishwasher discharging?
Where are the heating controls, pump etc?
The plot thickens!

First thing have you smelled the pool of 'water' that appears? Could it be from a dog, cat or errant husband sleepwalking after a night at the rugby club?

Ha! 😂😂 Sadly, no. No pets, and dh and I were both in the lounge at the time it appeared.

Heating system: we have a gas boiler in the utility room, a cold water tank in the loft, and hot water tank in the airing cupboard. Sorry if that's a bit clueless. No pressure gauge.

No, no washing machine etc on at the time. The dishwasher is in the kitchen and the pipe just goes under the kitchen sink and straight outside, so can't be that. The washing machine is in the utility room, on ground floor, so it would have leaked a long way before the water got to the stairs. It's fine.

Do the heating pipes pass through floor downstairs? Could the water be coming up rather than dropping from the ceiling above. I once visited a house several times trying to find the source of an intermittent leak. After breaking up the concrete floor for a distance of 25 feet the problem was found to be a built in dishwasher hose that had come out of its waste. Luckily the customers insurance company were very understanding.
If you suspect the heating pipe work, send someone into the roof void and tie up the ballvalve on the small tank. Leave for a week and then compare the water levels. Inspect the tanks for leaks while you are there.
Good luck!

Have you got trace detect cover with your insurance?