CH - Very small frustrating leak

[fezster]

I've spent the last few months trying to track down a gradual pressure loss in my CH and it's getting beyond frustrating.

Initially, I was losing 0.1-0.2 bar every day.

What I've done so far:

1. Checked every radiator valve - found a leak on one which has now been fixed.
2. Checked all Drayton TRV4's - found a few where water was being released when CH cooling down. Tightened gland seals and believe these are now fixed.
3. Checked relief valve is not discharing into tundish.
4. Checked condensate is not leaking when boiler off (HEX leak)
5. Checked EV pressure.
6. No visible signs of water anywhere on floor or ceilings
7. Tried wrapping tissue around all of the non-TRV valves to see if they are seeping. Nothing found.

I'm now losing approximately 0.05 bar every couple of days. So it is very minor and I imagine that whatever water is escaping is evaporating before I can see it.

Any further suggestions?

 

[terryplumb]

Any pipework buried in concrete floors or floor void ? Any pipework " boxed" in and not visible ?

 

[CBW]

Any air vents on pipework in loft, presuming you have one? Check all the Drayton TRV’s again.

 

[fezster]

Definitely pipework buried in walls and floor. However, not sure I'd ever know of such a small leak there. Any ideas?

There are AAV's but I've not seen any signs of water. It is possible residual air is escaping, but this has been going on for months, so not sure if that theory holds true after that length of time.

 

[HERTS P&D]

A thermal camera will find a leak in a concrete floor!

Or get a bottle of after shave and put it into the system and see where you smell it in a couple of days.

Andy

 

[Nige F]

You brut Andy

 

[fezster]

A thermal camera will find a leak in a concrete floor!

Or get a bottle of after shave and put it into the system and see where you smell it in a couple of days.

Andy

Do you think it'd find such a small leak? I've seen guys use them and it's usually quite difficult to distinguish between ambient heat - esp if we're talking tiny drips (although happy to be corrected).

 

[HERTS P&D]

As lang as you can put the heating on for a few hours , then a thermal camera can normally 'see' the leaking pipework.

Andy

 

[HERTS P&D]

What part of London are you in?

Andy

 

[fezster]

I'm in SE London.

Check all the Drayton TRV’s again.

Thanks for this suggestion. Even though, I had been regularly checking the TRV's - very time consuming with 30+ radiators, it does look like one of them was still weeping a small amount of water occasionally. It does seem to be only during cool down this happens and not every day. I've tightened this so need to give it a few days to check properly - but the gauge has dropped another 0.05 bar since Thursday (4 days).

How accurate are pressure gauges? Just wondering whether it's a little foolhardy relying on it to tell me small pressure losses.

As I understand it, the pressure on a gauge will rise rapidly when filling up until it hits the EV pressure. At that point, the EV takes up any excess pressure and so the volume of water going in is much larger above the EV pressure than below it. Therefore, if the gauge does drop to below the EV pressure, I'd expect there to have been a "considerable" volume of water loss and visible signs on ceilings or damp walls (with the exception of the pipework under concrete - which in my case, can be isolated, and I intend to do so as the next step to rule it out).

 

[CBW]

Yeah, wouldn’t rely on the gauge to give accurate pressure loss/gain, only if your losing lots of pressure or it increases.

 

[HERTS P&D]

I thought if you were in North London I could of popped in for you and used my thermal camera but I'm not going South.

Andy

 

[fezster]

I thought if you were in North London I could of popped in for you and used my thermal camera but I'm not going South.

Andy

Appreciate the offer, nonetheless