water meter continues to run...

[Completely Stumped]

Hi all,

New to the forum and would like to get some advice on something that's got me stumped. My water meter continues to run even when I'm not using water - we're talking just under 400mL of water per 6 hours or so (that's the longest I've managed to go without using water).

I managed to isolate the problem to the hot water system - if I turn off the inlet valve to my storage water heater, the meter stops running.

1. No leaking faucets
2. I got thermal imaging and ultrasound leak detection done by a professional - no concealed pipe leak detected
3. No visible sign of damage in my bathroom or leak from the water heater
4. Despite the running meter, I've had several plumbers/ contractors in for an opinion, and they all said a leak should have been obvious by now.

As a test, I turned the inlet valve off for 24 hours, and as soon as I turned it on, I immediately lost around 360mL of water.

Any ideas what this could be?

1. A leak that ultrasound was not able to pick up (apparently it's extremely sensitive, so I've been told this is not likely)
2. Some kind of weird problem with the storage water heater?

Obviously I would prefer not to have to hack into my bathroom wall unless absolutely necessary. I live in an apartment that is only about 3 years old.

Thanks all!

 

[oz-plumber]

Are you talking about less than 1/2 a litre of water over 6 hours?

 

[Completely Stumped]

Hi, yes less than half a litre over 6 hours

 

[Chuck]

Any ideas what this could be?

More details about the tank, please. Size? Model? Periods when it is heating. Storage temperature? Your normal pattern of water use?

I wonder whether you are seeing the supply 'topping' up the tank as it cools and the stored water cools (unlikely) and/or a pressure regulating valve that is 'passing' rather than shutting off hard.

 

[Completely Stumped]

More details about the tank, please. Size? Model? Periods when it is heating. Storage temperature? Your normal pattern of water use?

It's a 35L Joven (installed horizontally) - no idea about storage temperature (there is no dial that I can see). I generally only turn on the heater about 10-15minutes prior to a shower and then switch it off when done. The hot water goes to my hand basin and the shower only. I've turned off the hot water supply to the hand basin to make sure I wasn't inadvertently using "hot water" from the tank.

Just to note too - I've checked that there is no drainage from the tank from the pressure valve.

 

[Chuck]

It's a 35L Joven (installed horizontally)

Hmm. The only explanation I can think of that fits everything you've reported is that the Joven (or the outlet pipework has a couple of litres of air trapped in it. I'd rate this only as a 'possible' explanation, not a 'likely' one. Is the tank installed level? Are there any 'dead-legs' in the pipework between the tank and the tap / shower?

 

[PETE 123]

Some ideas, you got an overflow running or discharge on cylinder going somewhere.

 

[Completely Stumped]

Is the tank installed level? Are there any 'dead-legs' in the pipework between the tank and the tap / shower?

​

As far as I can see it is level. No deadlegs
[automerge]1598270393[/automerge]

Some ideas, you got an overflow running or discharge on cylinder going somewhere.

As far as I can tell - no
[automerge]1598270722[/automerge]

The only explanation I can think of that fits everything you've reported is that the Joven (or the outlet pipework has a couple of litres of air trapped in it.

Any suggestions on what I could try to test this out or fix this?

 

[SimonG]

I take it that the cylinder is unvented? Is it an internal air bubble or external expansion vessel?

 

[SJB060685]

Ok. So you have established that the fault lies downstream of the inlet valve to the cylinder.
Are you certain there is no discharge through the pressure relief valve?
I'm not not familiar with these units to be honest, I believe they're not a UK made product.
Is there an expansion vessel on cold inlet?
How long is the hot water pipework from the unit?