boiler losing pressure - no signs of a leak

[sunny12345]

hi all
my vailant boiler has been losing pressure at a steady rate (2 bar to empty in about 2-3 hours) for a few weeks now. i've had a boiler guy round and he said the boiler is fine, a plumber has been round and said there are no leaks at the rads, a leak detection guy round with his fancy toys but he wasnt able to find a leak. any ideas what else (if its not a leak) could be causing the pressure loss?
There's no water damage anywhere on the ground floor ceiling, ground floor floor board have been lifted and none of the pipes are leaking. the only place we can physically see is in the kitchen behind the units where the pipes are in the concrete floor. the leak detection guy did check there but said there was no trace of a leak...... i'm approaching my wits end so any help/advice would be appreciated

thanks in advance

 

[Gasguru]

What's the boiler make and model?

How many times have you topped up the pressure over the last few weeks?

Did the leak detection tech have all the gear..ie thermal imaging camera, tracer gases, sniffer etc?

 

[sunny12345]

hi, we are having to top up the boiler ever couple of hours.
yes the guy had the camera and the other bits

 

[sunny12345]

vaillant turbomax 828

 

[Gasguru]

Check the safety valve pipework for a start...that's a significant leak.

 

[Tay7]

Are the copper pipes buried directly in concrete?

Pipes direct in concrete ultimately fail.

How old is the house and piping? This could be the culprit.

 

[Gasguru]

Is this really a Turbomax? or a Turbomax PLUS or Ecotec etc. Is it condensing?

 

[sunny12345]

PRV is completely dry
pipes are under the concrete for about 5m - from the boiler in the kitchen up to the front room where they come out under the boards.
pipes have been in concrete for at least 20 years

 

[sunny12345]

its a combi boiler.... i can check the exact model this evening

 

[Gasguru]

Need to know whether this is a condensing boiler....ie the leak could be going down the condensate pipe....on a Vaillant this is the plastic pipe on the RHS. To check the concrete the water should have been removed from the pipework and the tracer gas pumped in.

 

[sunny12345]

RHS?
yes, the water was drained and the tracer gas was pumped in but i was told there nothing was detected in the kitchen

 

[Gasguru]

Right hand side

 

[sunny12345]

ahhhh duh lol..... no visible signs of a leak around the boiler. all pipes etc have been checked

 

[ianmcd]

No what Gasguru is saying is that the primary water may be leaking into the condensate collector and running through the condensate pipe , this would not be visable you will have to disconnect the condensate pipe, (white plastic one) and with the boiler pressurised and turned off if there is water dripping or in your case a very fast drip as you have a significant leak , then you need a new heat exchanger.

 

[stardanny]

Did the boiler guy do the check by turning off the flow and return isovalve under the boiler to rule out leak inside boiler?

Daniel.