Finding a hidden water leak

[MikeToll]

I noticed my monthly meter reading had gone up a bit so I’ve been taking more frequent readings and found the house is using half a litre of water an hour when the house is dormant with no known or intentional water usage.

There are no taps dripping (incl the outside tap), the 2 loft cisterns aren’t overflowing, no toilet is overflowing down the pan, no sign of a water leak at the gas boiler, washing machine or dishwasher, no soggy carpets under radiators, no damp patches of wall or ceiling and no musty smells anywhere.

If I turn off the main stopcock in the house then the water meter stops and shows no consumption/flow.

As there are no clues then I'm assuming the leak is probably from a joint that’s leaking into the external wall cavity and draining through the foundations, but I’d welcome other theories.

So I’m now stuck as to what to do next to diagnose the problem other than wait until something bad happens/appears.

Can anyone help with ideas to further diagnose?

TIA
Mike

 

[HERTS P&D]

Any push button toilets?

Andy

 

[Stuckinarut]

Do you have isolation valves to taps and toilets? Is the boiler pressurised and does it lose or increase pressure?

 

[MikeToll]

Any push button toilets?

Andy

The mind boggles but no, none of those

 

[MikeToll]

Do you have isolation valves to taps and toilets? Is the boiler pressurised and does it lose or increase pressure?

There are isolation valves - they're mainly close to their outlets and visible-to-the-outlet so I can see no leak beyond those, but I'll check for ones that might be used to diagnose further - good thought - thank you.

The boiler has a F&E tank so I'm assuming that makes it an unpressurised one.

 

[Stuckinarut]

There are isolation valves - they're mainly close to their outlets and visible-to-the-outlet so I can see no leak beyond those, but I'll check for ones that might be used to diagnose further - good thought - thank you.

Yes, I was thinking if you start isolating things and monitor it, you may just find the cause.

The boiler has a F&E tank so I'm assuming that makes it an unpressurised one.

Yes, this is correct

 

[MikeToll]

Is it possible to track down a "half litre an hour" leak with a stethoscope or other listening device or would the leak be just too quiet to find that way?

 

[Stuckinarut]

Is it possible to track down a "half litre an hour" leak with a stethoscope or other listening device or would the leak be just too quiet to find that way?

I suppose it depends where it's leaking from and if making any noise

 

[Lower]

Is it possible to track down a "half litre an hour" leak with a stethoscope or other listening device or would the leak be just too quiet to find that way?

half a litre per hour is the equivalent of a drip every 2-3 seconds so unless you can hear the drip falling onto something you won't be able to hear the water movement in a pipe.

I'd start by tracing all the pipework around the house to work out where it goes and then start looking for dampness both inside and outside the house in the areas where the pipes run or below.

Are you sure there is no water leaking into the toilet? Put some toilet paper on the back of the bowl above the water line to see if it gets wet.

 

[YorkshireMidge]

You mention water down a cavity, and you also mention you have an outside tap. Did you protect your outside tap from frost over winter? If it has frozen up, it could have split the pipe within the wall. That being said, 0.5L/hour seems too low for a pipe split at mains pressure.

Any other part of the house where there is water pipework outside of the main building structure? We have two such areas - an integral garage with a sink in it and well lagged pipes, and a downstairs loo - and both stand proud of the main structure of the house so tend to be cooler. It is significant that the only place we have ever had a split pipe was the downstairs loo where the pipe insulation the builders had used was rubbish.

Anything screwed or nailed to walls recently?

You say there is no leak from the washing machine/dishwasher - but have you turned the isolating valves off just to be sure? Never had the issue myself but I have heard of inlet valves going a bit iffy and not fully shutting off and allowing the water into the appliance even when it is switched off. I'd have expected signs of that within the appliance with the water volume you're talking about though.

 

[MikeToll]

Are you sure there is no water leaking into the toilet? Put some toilet paper on the back of the bowl above the water line to see if it gets wet.

Yes that's part of my monthly checks when I do the meter readings ... I've had 2 such leaks in the past so I've learned the lesson!

You mention water down a cavity, and you also mention you have an outside tap. Did you protect your outside tap from frost over winter? If it has frozen up, it could have split the pipe within the wall. That being said, 0.5L/hour seems too low for a pipe split at mains pressure.

Any other part of the house where there is water pipework outside of the main building structure? We have two such areas - an integral garage with a sink in it and well lagged pipes, and a downstairs loo - and both stand proud of the main structure of the house so tend to be cooler. It is significant that the only place we have ever had a split pipe was the downstairs loo where the pipe insulation the builders had used was rubbish.

Anything screwed or nailed to walls recently?

You say there is no leak from the washing machine/dishwasher - but have you turned the isolating valves off just to be sure? Never had the issue myself but I have heard of inlet valves going a bit iffy and not fully shutting off and allowing the water into the appliance even when it is switched off. I'd have expected signs of that within the appliance with the water volume you're talking about though.

Yes outside tap is protected and no other pipework is external ... apart from loft overflow ends.
No, no recent DIY ... and I've not put a drill through a cold water pipe for years ... tho it was spectacular and I did get soaked running to the stopcock.

With the appliances I was thinking that any water would have to pool inside them because the outlet hose is raised 2-3' to the outlet pipe... no sign of pooling in them.

My thanks to all of you for talking it through with me because it gets me to a stage where at least I have a plan:-

1. Check if isolation valves allow progress on diagnosis.
2. Borrow thermal camera and have a good look around outside and inside.
3. Monitor water meter for any worsening once a fortnight (initially).

 

[YorkshireMidge]

@MikeToll The only other personal experience I have that springs to mind is this one:

C/H pipe crusty and leaking

Just noticed a couple of small brown stains on the kitchen ceiling today, from our main bathroom above. I was expecting a leak somewhere, but not the one I actually found - which is a very crusty looking central heating pipe under the bathroom floor. I can't actually get to this from above as...

www.diynot.com

Two lessons I learnt from this:

1. The only clue to the problem was a couple of tiny stains no bigger than a 10p bit along a plasterboard seam in the kitchen ceiling below about a foot from the wall - and when you see the amount of water on the upper side, it was clear it must have been draining off the edge of the plasterboard and down the cavity. You could be looking for a similarly tiny clue but I suspect it will be there somewhere.

2. Because I had to cut a hole in the ceiling to investigate, and I was reasonably sure it was a C/H pipe in that location, I remember checking the C/H header tank first and not seeing any drips from the float valve and starting to doubt myself. In hindsight, I think I'd just checked at the wrong point in time where the valve had recently closed (because the flow of water filling was much greater than the leak) but before the water had dropped again for the valve to start to open. I suspect if I'd just stuck my finger under the nozzle of the float valve, I'd have found it was damp and that would have prompted me to watch for a few minutes where I'm certain I would have then seen the float valve open.

 

[MikeToll]

Good case study - well found and well fettled.
I'll take those 2 nuggets of learning and apply them - many thanks

 

[mcmoby69]

Pinholed coil on the cylinder?
Chuck a teaspoon of drain dye into the CH header tank. See if your hot water changes colour. Might take a day or two.

 

[MikeToll]

Pinholed coil on the cylinder?
Chuck a teaspoon of drain dye into the CH header tank. See if your hot water changes colour. Might take a day or two.

Ooh interesting thank you - that'd be a sneaky leak, tho' the drain dye technique and a month or more of fluorescent yellow baths might incur the wrath of Mrs Toll.