How many plumbers does it take to find a central heating leak? Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[punchdrunked]

Good afternoon all.

I've specifically joined this here forum for guidance, help and clarification when it comes to who should be best qualified to find a leak in my central heating system.

Back story first: Turned the heating on - one of the radiators was hot on the bottom, luke warm on the top, so I bled the radiator and then noticed the boiler pressure was at zero. Adding water to raise the pressure to 1.5 bar and water started gushing out of the base of the machine. The saga starts from here.

Corgi engineer comes out for first visit. Sucks in teeth and states that because it is a Veismann boiler (Vitodens 100) it'll be best to call them out. 2 x Veismann engineers later, an expansion vessell replaced, a pump replaced and the circuit board replaced - the pressure is still dropping to zero when the central heating is not isolated. His view, a massive leak somewhere under the ground floor piping - no evidence of a leak visible. Will need trace and access.

So, I paid 2 x leak detection companies (£1k in total), only to be told that Nitrogen was escaping from he flue that exits the boiler - his view is that the heat exchanger is toast. No other gas escape in the property, just the flue (50% reading)

What is my point? 5 x gas safe engineers claimed it was a leak in the pipes under the floor boards (because of the pressure drop). Leak detection says don't pull up floorboards, the boiler is your problem.

Who is right? Corgi are coming out again.

[stoneyboy]

Hi punchdrunked,
What a sad and difficult problem - you have my sympathy.
Reading between the lines you are able to isolate the heating circuit flow and return at the boiler. If you have done this and the water pressure remains as set I would suggest the leak is in the heating circuit, somewhere. Presumably with the heating circuit closed off and you set the system to heating for a short period, the pressure remains so the heat exchanger is not the issue.
With the air we breath being nearly 80% nitrogen I doubt a 50% level in the flue gas is relevant.
If you have pipes enclosed/buried in your house structure it’s best to guess pipe routing and see if you can detect moisture. Pipes under wooden floors are easier because you can lift boards to investigate. Good luck.
Regards S