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Discuss Water usage - why is it so high? in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Hi all
This is only about my third/fourth post, so go easy. Also, I'm only an enthusiastic amateur, not a pro...

I'm having issues with the waterboard and can't work out what's happening. For the past three months, they're saying we're using a huge quantity of water - 700 litres per day at least. We've been in the house for 10 years, so we know that typically we use c.400 litre per day. Over the past few six month periods (three or four periods, I think) they had to average our bills, as there was a water leak down the road, so everyone in the road had an incorrect reading for almost two years.

From October, our plumbing set-up was completely changed, as we've rebuilt the entire house.
We've gone from:
Mains pressure (6.5 bar), combi boiler, c.15mm (actually imperial, so I think that's half inch) supply pipe from the metre. Our flow rate was 15-20 litres per min (according to the outside tap). We had one family bathroom with a bath and one ensuite with a main pressure shower (no bath). 15mm copper piping everywhere. GFCH and rads.
Washing machine - Miele c.2008
Dishwasher - Miele c.2008
Outside tap

To our new system:
New gas boiler
UVC for the hot water, which is fed via a copper loop (with a pump) - but regulated to 3.5 bar
New water softener - Kinetico- appears to circle/clean c. one a day for about 12mins. It's one that only softens what it uses, it's not an electric one that cycles regardless
Same washing machine
New dishwater
Cold water for the house is also on a loop - 20mm pex-al-pex which feeds to manifolds by each bathroom/kitchen taps and then we have 16mm pex-al-pex to the various appliances/taps
We have a low-loss header and an expansion vessel thing. I have no idea what they are though.
We also replaced the pipe from the metre to the house with a plastic metric one - I think it was a 28mm or 32mm, can't remember
Mains pressure is still 6.5 bar, but is regulated to 3.5, as I say
We're only using one bathroom at the moment (I'm still installing the others) and that's got a bath, shower and basin.
There's a temporary bathroom outside for the builders - one of them lives with us. It's got a small water heating vessel that takes about 30 litres and the cold comes from the house (no leaks that I can see).

Here's what I've done to investigate so far:
Had the water metre replaced
Turned the water off overnight (inside the house) - no usage recorded by the metre
Read the metre morning and evening every day (and now I'm just doing it every morning)
Turned off the stopcock to see whether the metre was still recording usage (in the day) it wasn't
Checked everywhere for leaks - as the house is only half built I think we'd notice the extra 300 litres that we're trying to identify
Checked the flow rate on the shower, it's about 10 litres per min
Listened to the stopcock while everything's off - nothing sounds like it's flowing

Our water usage is typically:
Wife and I shower each morning for an average of 8 and 6 mins respectively
Kids bath every other day - new bath is 1800mm (100mm longer than previous). However, previously - as they were younger - they bathed every day - so our usage should have dropped, if anything
The builder that lives with us has a skin condition, so he only showers once or twice a week. Previously to the high bills, we also had one or two of his labourers living here too - so again, our usage should have actually dropped
We don't water the garden, it's full of hardcore
We filled up a paddling pool twice this year. I reckon it's about 150-250 litres tops
There are no huge quantities of water being used for the building. The concrete was mostly done in 2020 (and ready mix in the main, anyway) and the plastering was done a long time ago (and again, wouldn't account for 300 litres per day, surely...?)
We run the dishwasher probably 9 times a week and the washing machine potentially about the same

What I'll try next:
Isolating the water softener for a week or so
Attaching a water metre inside the house - just after the stopcock to start with, then potentially to each manifold, so I can see whether one particular area is contributing to usage more than another by taking regular readings
The waterboard have said they'll send someone out with a listening device to check for leaks
I wonder if I'll have to dig up the connection we made to the metre with the new pipe. Our plumber did it and the experiment I did in turning off the water overnight (which recorded no usage) suggests that's not the problem though

My wife and I have been working from home during Covid, but I already worked at home three days a week before Covid hit and my wife's work was similar.

Here are the metre readings I've taken in the past week or so:

Day | AM/PM | Reading | Increase | bath night?
Mon PM 6.1 0
Tues AM 6.1 0
Tues PM 6.7 0.6 Bath
Wed AM 6.8 0.1
Wed PM 7.2 0.4
Thurs AM 7.3 0.1
Thurs PM 7.8 0.5 Bath
Fri AM 7.9 0.1
Fri PM 8.5 0.6
Sat AM 8.7 0.2
Sat PM 9.0 0.3 Bath
Sun AM 9.2 0.2
Sun PM 9.6 0.4
Mon AM 10.0 0.4
Tues AM 10.3 0.3
Wed AM 10.8 0.5 Bath Tues PM

Southern Water is our waterboard. I'd be really grateful for anyone's experience/expertise as to what this might be, please. Anything else I can try..? We're on a septic tank, but I don't see how I can measure what's leaving the property...


Gas Engineer
I would say the extra may come from the builder? Does anyone leave taps running when cleaning their teeth? Have you checked any toilets for running overflows? - modern ones run into the pan.
I would say the extra may come from the builder? Does anyone leave taps running when cleaning their teeth? Have you checked any toilets for running overflows? - modern ones run into the pan.
There's been a small amount of plastering over the past few months, but otherwise, it's been things like kitchen install, (pre mix) rendering etc. Nothing that uses that kind of quantity as far as I can tell. We all shut off the taps when we're brushing out teeth.
Thanks re loos - I haven't checked the loos for that, no. Never heard of it. How do I do that, please? Is that something I'd just hear and is constant (in which case I don't believe it's happening)?

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