Valiant Ecotec Plus 938 A - Losing pressure (losing my mind!)

[Justin01981]

Good afternoon. I am hoping someone may be able to help with an issue I have on a Valiant Ecotec Plus 938 boiler. Fitted approx 4 years ago, the boiler has been suffering from the loss of pressure on the system (down to 0) at least once a day, typically when it is not in use. I have so far;

1. Had the pipework checked for leaks with ADI Leak Detection - no leaks found
2. Pressure Release Valve replaced
3. Valiant attend who advised it was the Heat Exchanger
4. They have replaced this and the AAV

As this did not work Valiant engineer has advised it is due to the gas pipework to the boiler not being large enough and it should be increased from 22mm to 28mm. This makes no sense to me as;

a) the inlet to the boiler is 15mm so the current pipe is already larger than the boiler can take (it is reduced to 15mm at the boiler for connection)
b) even if the gas inlet pipework was considered too small, how would this cause the boiler to lose its pressure on a regular basis

I have escalated it with Valiant who is due to call me back but wanted to see if anyone on here may be able to confirm if the above 'diagnosis' as to the gas pipework size has merit and what other possible causes it may be?

I would appreciate any help!

 

[Ric2013]

Gas main being potentially undersize (assumption A is incorrect - a 15mm inlet boiler might require a 22 or 28mm pipe run depending on the nature of the pipework connecting it to the meter) would not cause water leakage and consequent drop in fill pressure (assumption B is correct).

I'm assuming the expansion vessel has already been tested for correct operation and precharge?

 

[Scott_D]

Isolate flow and return valves for as many hours as possible (don’t use the heating)
If pressure drops on boiler - boiler leak
If pressure drops on system - system leak

 

[ShaunCorbs]

As above need to isolate boiler