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

 

[Chris80]

Thanks Best. I'll give that a go as soon as poss (the wife likes having hot water) and let you know. I think it'll need a day and a half to run totally cold as we only heat for 1 hour each day at the moment.

 

[Best]

Yes, you shouldn't have the water meter moving if no water used. Leaks should not exist, even microscopically on fittings on pipes etc, but things like toilet fill valves and especially toilet flush valves cause a lot of unnoticed leaks on cold supplies.
I am lucky over here, so far, as ordinary households do not have meters and I can use as much water as I want. New valves on roads are fitted though, which have the provision for a meter. :smile:

 

[Chris80]

Thanks for all your advice. Too true about meters. If I didn't have one I wouldn't need to have given this a second thought as there is no sign of a leak. Really seems you've helped me confirm the usage is the Megaflo and likely to be normal. Cheers and I will update this thread in the near future.

 

[Chris80]

Just an update as promised. We went on holiday for a week, had the mother in law in an out to feed the cat etc so couldn't fully monitor the meter. Used around 6 litres per day which seems about right for a one visitor per day. This was the only opportunity to allow the hot water tank to get stone cold. On return checked the meter and again after half an hour or so and no movement at all. This seems to conclude that the water use is a function of re pressurising the hot water cylindricer as it cools. So don't think there is any specific problem. Would be interested to know if other similar systems do the same thing. Cheers.

 

[Best]

Thanks Chris for reporting back.
Yes, all unvented cylinders will do same, because hot water is expanded & will become less volume when cooler. If you put warm water in a plastic bottle & tighten the top on, - you will find the plastic bottle will gradually crush in. If that bottle was an unvented unit, the water would be replaced by the mains joined to it.
You have just been vigilant and found this.

 

[Chris80]

Thanks Best. Another query please. Just today I have noticed water dripping from the water tank overflow outside. Just started as the water is heated. This means time to recharge the air gap. All ok but it is 3 months since the last time and I think 3 months before that. Is this normal? Cheers.

 

[Best]

Hi Chris. You should speak to Heatrae Sadia & ask them about your Megaflow needing the air gap done every 3 months. I hear the floating baffle needs to be checked.
If all else fails, a properly sized external expansion vessel could be fitted by a G3 engineer, but that would be better by instruction of Heatrae Sadia (Megaflow). Your Megaflow I think will have a 25 year warranty providing it has full yearly service record, but this will only cover the main unit.
It is also possible that you have coincidently suddenly too much pressure to the unit, for example, and the proper air gap perhaps still intact and therefore not the cause. Needs a G3 plumber to check. Don't try working on it yourself, except the air gap recharge.

 

[Chris80]

Thanks best. I called megaflo last time and they weren't able to service my tank as it is over 10 years old. Bizarre, but also didn't do 25 year guarantee when mine was installed some 15 years ago. If I recharge it and it doesn't overflow through the tundish this presumably means the pressure is ok? If not is there a register of G3 engineers? Cheers for your help. Much appreciated.

 

[Best]

If you recharge the air gap and the discharge stops for weeks, then the air gap must have been deplemished. But won't prove anything else.
Not sure about how you would get a G3 plumber tbh. A fair number of plumbers probably are now G3 qualified, as they need to be to install and do the paperwork for notification & warranty on unvented cylinders, let alone even service or repair them.
If you still are having bother with the discharge I suggest you go with the idea of a expansion vessel fitted by a G3 person. Megaflows are too expensive & if you need to replace it there are many cheaper units.