Very slow movement on water meter but no leak found

[Chris80]

Hello

I am hoping for some advice please. I have recently noticed that my stop tap under the kitchen sink is really tight, so to check we can isolate the supply in an emergency I turned off the stop tap in the road - all OK. However, when turning it back on I noticed the 0.0001 dial is turning very slowly (so much so I reckon many wouldnt have noticed it). I have therefore managed to turn the stop tap under sink off (using a spanner and a lot of force) to fully isolate the internal water supply, there was then no movement on the meter so it seemed small internal leak. I have since done all of the following and the meter i still turning ever so slightly:-

• Replaced kitchen tap valves (as the tap was dripping)
• Changed old toilet filler and flush (as the filler would drip for ages after the main fill)
• Put food colouring in other toilet to check for leak - no leak into pan
• Isolated cold water supply to Megaflo hot tank (unvented so no cold header in loft) to rule out the hot water system
• Turn off isolator valves to dishwasher, washing machine, other taps etc.

The blasted meter is still moving ever so slightly, so overnight I have checked the meter at 11pm and then 7pm with zero water use and it is registering about 600ml used - so not a lot. Is this minimal movement normal or do I have a leak? There are no stains or sounds etc, I am at a loss so any advice or opinions are gratefully received.

Thanks

 

[brum]

you have a leak somewhere mate..brum

 

[oz-plumber]

The only way you are going to find a leak that small - if there are no visible signs - is to disconnect the house side of the stopcock under the sink and pressure test the house plumbing and then pressure test from the stopcock back to the meter.

Your losing less than 2 litres of water a day, if the leak was inside your property you would have some visible signs of where the leak is.

 

[rpm]

Heard of one this week where the leak was traced to a plastic pipe in a stud wall.

 

[brum]

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I would guess leak in partition or under floorboards down stairs oz is right a pressure test would confirm this I have heard of engineers hooking on CO2 and listening out for the whistle to locate leak position..brum

 

[Chris80]

Thanks guys. To confirm the ground floor is concrete so I am assuming there is no plumbing under there apart from the main water supply? The house is timber frame so I was thinking any leaks would be more evident?

I have had the stop tap off for 3 hours today whilst we were out. Came back and turned back on and ran around listening for water filling. The only area I could hear it was in or around the megaflo. When turning the cold supply megaflo tap off it stopped. This brings me back this but when turning tap off in the last few days the meter keeps turning slowly?

Thanks so far. At the moment I am thinking pressure test (thanks for the advice) but still troubled why the megaflo seems to refill after cutting water supply but the tundish and overflow to outside is dry at all times.

 

[Deleted member 7121]

Thanks guys. To confirm the ground floor is concrete so I am assuming there is no plumbing under there apart from the main water supply? The house is timber frame so I was thinking any leaks would be more evident?

I have had the stop tap off for 3 hours today whilst we were out. Came back and turned back on and ran around listening for water filling. The only area I could hear it was in or around the megaflo. When turning the cold supply megaflo tap off it stopped. This brings me back this but when turning tap off in the last few days the meter keeps turning slowly?

Thanks so far. At the moment I am thinking pressure test (thanks for the advice) but still troubled why the megaflo seems to refill after cutting water supply but the tundish and overflow to outside is dry at all times.

Could be be the hot that's leaking and that's why megaflo is filling

 

[Chris80]

Thanks pipe man. I previously thought I had ruled out hot water leak as when isolating the cold feed to the megaflo the meter stills turns slowly.

 

[lame plumber]

just check if you have any storage tanks in the roof, isolate them first and then see if the movement stops, they are the normal cause of your issue, otherwise check your wcs arent leaking out into the pan via a duff syohon.

 

[Chris80]

Thanks for that lame plumber. But I don't have a loft tank and I have checked all the toilets. I'll have to get a plumber in to find this phantom leak. The others have recommend a pressure test so I'll ask for that. Always like to diagnose things myself but struggling on this one.

 

[IDCHAPPY]

Megaflo unvented hot water cylinder? have you checked the tun dish to ensure its not passing and thus refilling the cylinder?

 

[Chris80]

Hi there. The tundish an outside discharge is dry as a bone. Cheers.

 

[Best]

Hi. If your Megaflow cylinder refills (repressurises) after you turn the water on to it, then if no hot outlet is passing & tundish is dry, it could simply be explained that it's due to the hot water cooling a bit in the unit & this will mean the water pressure will drop a little & unit pressure will need to recover to whatever the pressure reducing valve set limit is.
By that I mean - lets say your prv is set at 3 bar, then that means the cold pressure inside the cylinder is 3 bar. That will rise a little over 3 bar when the Megaflow water is heated & only drop back to 3bar if a hot tap is opened. But hot water at 3 bar will drop in pressure as it cools. Then you turn mains back on & it refills.
Toilets are the biggest cause of water loss.

 

[Chris80]

Thanks Best. That seems really sensible. A query please, if I turn off the main stop tap for a couple of hours and turn it back on you can hear water entering the megaflo (to repressurise by the sound of it), however if I isolate the cold water fill tap (red tap in the picture) but not the main stop tap, even overnight, the water meter keeps moving very slowly. Does this mean that to repressurise the megaflo takes water elsewhere (rather than the cold fill)? Is 40ml to 600ml per hour seem normal? Many thanks.

PS I assume the pressure gauge shown is in fact for the heating pressure.

 

[Best]

Hi Chris. That red headed valve in the picture is a gate valve. It really shouldn't be used on cold supply to your Megaflow IMO.
A brass stopcock or large lever ball valve (full flow) are much better as they will shut off fully. Gate valves are notorious for letting water pass slightly, especially on high pressure mains.
It would be advisable to have the Megaflow isolated so to rule it or hot pipe work out for leaks. I prefer lever valve.
It is also possible that you might have a mixer tap or shower valve letting unbalanced cold mains through its body & this will pass to cylinder & raise the pressure. That however, would simply stop at whatever pressure the mains is, or if high enough, go out tundish.