High water usage - unvented cylinder?

[Nigel A]

Hi there,
A common question I'm sure: "Why is my water usage so high?". But bear with me - I'm open to any feedback or ideas.

Problem: Our smart meter is indicating that we currently use 44l per hour, even when we're away for the weekend, and even when it's 3am in the morning. The meter (a thames water sensus) is installed at the boundary of the property.

The usage increase started approx October 2021 and has been steadily getting worse and worse.
FYI The last physical plumbing activity was around March 2021 time, when a new 'Main' unvented cycliner was fitted and new bathrooms and toilets installed.

1. When I close the mains stop valve for an hour, the meter reading doesn't doesn't increase. So presumably no leaks between meter and house.
2. There's no leaking toilets or dripping taps.
3. The external taps are turned off.
4. The only water-based devices actively running when we're not here:

• Boiler and "Main" unvented cyclinder.
• Wet underfloor heating.

both seem to be operating fine.

I'm at a loss as to what is using water 24/7. I'm not a plumber, but I'm a pretty logical person and this feels strange to me.
Q) Do either of the 'cylinder' or the underfloor heating have a 'waste pipe' and that could be continually leaking water? How would I check

Any other ideas??!

 

[BlueLoo]

It is not clear if this flow rate is evident when you think you have everything OFF.

Why is the 44L/H coloured brown in the chart? Is this perhaps a notional rate to pay for the supply itself? (dunno tbh)

 

[polesapart]

Got one of these in your airing cupboard? Is it wet?

 

[Harry Bloomfield]

That is an impossible amount of water usage or loss per hour. It makes your weekly consumption around 796525 x that of our weekly consumption. You simply cannot get much volume to flow through a domestic pipe and if it did, the whole neighbourhood would be under water. Either your meter is wrong or your reading of it.

 

[Nigel A]

It is not clear if this flow rate is evident when you think you have everything OFF.

Why is the 44L/H coloured brown in the chart? Is this perhaps a notional rate to pay for the supply itself? (dunno tbh)

The chart is from Thames water's website. As far as I can tell, the brown 44L/H is highlighted to indicate to the user the minimum hourly rate for the day.
I don't think it's the notional charge, though I'm going to go and check the tariff right now.

 

[Nigel A]

Got one of these in your airing cupboard? Is it wet?

Hi polesapart,
Thanks for the reply!
Yes we have one of those next to the cylinder but no it's not wet - it's completely dry.

 

[flameport]

) Do either of the 'cylinder' or the underfloor heating have a 'waste pipe' and that could be continually leaking water? How would I check

Cylinder does, as in the picture above.
The UFH, boiler and related items do not, any leak there would result in the pressure dropping to zero very quickly and the boiler would stop working.

There's no leaking toilets

Check again - it's common for the flush mechanism to leak due to age/limescale, and the result is a thin film of water running down the back of the toilet bowl. Nearly impossible to see, but easily identified by flushing the toilet, waiting 10 minutes for the bowl to dry, and then placing a piece of toilet paper at the back of the bowl.

 

[BlueLoo]

The chart is from Thames water's website. As far as I can tell, the brown 44L/H is highlighted to indicate to the user the minimum hourly rate for the day.
I don't think it's the notional charge, though I'm going to go and check the tariff right now.
View attachment 258620

Ah, ok.

seems rather flat for a leak

 

[Nigel A]

That is an impossible amount of water usage or loss per hour. It makes your weekly consumption around 796525 x that of our weekly consumption. You simply cannot get much volume to flow through a domestic pipe and if it did, the whole neighbourhood would be under water. Either your meter is wrong or your reading of it.

I know, right?! That's why I just don't get it 44l would hardly be un-noticable, as you say.
It's thames water that is reading the meter (smart meter). The readings on their website correspond to the reading on the device itself.
I suppose the meter _could_ be broken somehow? Depending on feedback to this post, I may raise this with Thames Water once I've ruled out any issues in house.

 

[flameport]

There is another possibility - someone has left the filling loop for the boiler open, and it's constantly filling and the water is being let out of the pressure relief valve, which may not be in an obvious place.

Check at or near the boiler for a silver braided hose with a valve on each end, both should be closed. Post a picture of what's there if unsure.

 

[Harry Bloomfield]

The chart is from Thames water's website. As far as I can tell, the brown 44L/H is highlighted to indicate to the user the minimum hourly rate for the day.
I don't think it's the notional charge, though I'm going to go and check the tariff right now.

That's more like it. You suggested 44m3 per hour, in fact it is 44L per hour. 1000 times less. That is 12672L per week, or 12.672M3 compared to our 1.4M3 per week. Still a lot.

Turn your stop valve in the house to off, check the meter to see if it stops counting - if it does the leak is your house, if not the leak is from the pipe between meter and house.

 

[Nigel A]

Ah, ok.

seems rather flat for a leak

OK I just checked the bill. I can't see any indication of a 'notional charge' - aside from the flat 'service charge' which is minute in comparison.
The 228m3 indicates consumption.

 

[Nigel A]

That's more like it. You suggested 44m3 per hour, in fact it is 44L per hour. 1000 times less. That is 12672L per week, or 12.672M3 compared to our 1.4M3 per week. Still a lot.

Turn your stop valve in the house to off, check the meter to see if it stops counting - if it does the leak is your house, if not the leak is from the pipe between meter and house.

SORRY! That was a terrible typo. 44L per hour, not m3 as you say
When the stop valve is off, the meter stops.
So the 'leak' is in the house - but I'm at a loss as to what I can check beyond toilets and taps, which I've checked.

 

[BlueLoo]

Can you open up the manholes?

Have a look to see if water is flowing?

 

[Nigel A]

There is another possibility - someone has left the filling loop for the boiler open, and it's constantly filling and the water is being let out of the pressure relief valve, which may not be in an obvious place.

Check at or near the boiler for a silver braided hose with a valve on each end, both should be closed. Post a picture of what's there if unsure.

Hi flameport,
Thanks so much for the reply.
The filling loop is closed if I read this correctly: