Gravity system drawing water from mains

[Canyouhelp]

Hi all,
Any ideas what would cause a constant draw on the cold mains on a open vented gravity pumped system?

I noticed today that the water meter is going round consistently and pin pointed it to the heating system as only does it when pump is running. There's no valve letting by in tanks . I assumed a pipe leaking but all dry and nothing below floor at ground level. Meter is in kitchen behind unit and all pipe work dry. No overflows leaking and no toilets letting by or taps dripping so as said deffo on the heating somewhere?

Any ideas would be a great help as its got me stumped

 

[seco services]

Delete.

 

[Jackrae]

Where's your meter, inside the house or out. If outside, close your stop-cock where the water comes into the house. Does this stop meter: if NO go back to square one. If YES then either there is a leak between meter and your stop-cock or some-one else is drinking your water.

 

[echoes]

How much water is being used? It must be going somewhere after the meter.
Is it a vented hot water cylinder and open-vented heating system (2 loft tanks)?
Can we eliminate the obvious by being sure it's the water meter going round and not the gas meter?

 

[Canyouhelp]

Meter is inside, draw is definitely after meter and only occurs when the heating pump is running There is no pipe work below floor level and no wet areas above floor level no obvious signs anywhere.

I was wondering if the pump could somehow be pulling water through from the cold feed but can't figure how it could?

 

[Canyouhelp]

Two tanks in loft, so twin vented and neither ball valves are operating whilst this is happening.

Yes we can rule out the obvious, it's the water meter not the gas. Not sure what the meter is reading in on the unit of M3 as its got 4 black digits and then 4 red so presume the last digit is 0.1litre and therefore it's using approx 0.1 L about every min!???? So a lot in my opinion .

I will expose all the pipework tomorrow as all the drops are boxed in where coming downstairs and then the rad feeds pop out in the horrid 10mm microbore crap and run surface to the rads so almost all is visible. Due to its runs I'd expect to see a leak if there was one, which is why I thought maybe the pump is somehow causing it as meter stops when pump is stopped?

 

[Canyouhelp]

Two tanks in loft, so twin vented and neither ball valves are operating whilst this is happening.

Yes we can rule out the obvious, it's the water meter not the gas. Not sure what the meter is reading in on the unit of M3 as its got 4 black digits and then 4 red so presume the last digit is 0.1litre and therefore it's using approx 0.1 L about every min!???? So a lot in my opinion .

I will expose all the pipework tomorrow as all the drops are boxed in where coming downstairs and then the rad feeds pop out in the horrid 10mm microbore crap and run surface to the rads so almost all is visible. Due to its runs I'd expect to see a leak if there was one, which is why I thought maybe the pump is somehow causing it as meter stops when pump is stopped?

 

[Jackrae]

Central heating system should be TOTALLY isolated from the mains system with the header tank acting as the only means of getting mains water into the heating system. Unless your "plumber" has somehow got his piping screwed up. Is there any chance the relief valve on the boiler is passing or is the boiler producing an excessive amount of steam when it's firing - indicating a possible leak into the boiler system.

Another, very remote, possibility is what in the oil metering industry we used to call "electronic oil", but it will only apply if you have an electronic meter. If there is a pulsation in the mains water system it can "rattle" the impeller that is used within the meter such that the impeller blades are being seen as moving, hence the meter clocks up even with no flow.

 

[Canyouhelp]

It's all piped up ok. The boiler is an old un... Potterton floor standing 14kw, A relic really I suppose but works ok and does the job.

I switched the boiler off yesterday and noted the meter reading checked it this morning and meter at same reading. So all a bit bizarre as all weekend the meter has been slowly going round and as previously said, without any water been used but stopped as soon as turned heating off.

On thoroughly checking all pipework and valves on rads I found a small weep has been occurring and so have replaced this valve so I will leave it on and monitor it again.

The rad that the valve was leaking on was also not getting as hot as the rest by about 20 deg difference and water in it was a bit black so I flushed it out.

I can only assume that maybe this was the cause? and in turn was causing the header tank to very slowly top up the system . As the pipework to the rad is microbore and running along the top of the skirting , the water from the weeping valve has been soaking into the wall and behind the skirting and as this is also on the ground floor would not be seen or noticed.

So far it's not done it again.

Thanks though to all who replied .

 

[onecog]

I see you live on the Isle of Wight.......Freshwater by chance?