Boiler pressure rises only when heating is on

[Emu13]

Hi everyone,

I have Vaillant EcoTech boiler that's been fine during the summer, but now that's Winter I'm having to drain approx 2 litres from the heating circuit every 1-2 days. I'm puzzled to understand why. Simple logic tells me that if the filling loop was slowly leaking water into the heating circuit then the pressure would rise regardless if the heating was on or not. For your information, the pressure doesn't return to normal levels after the system cools, but does return marginally lower.

I welcome any ideas.

Regards

 

[ianmcd]

If the pressure only rises when heating is on, it is an expansion problem,if you are saying that you have to drain the boiler and not top it up then the Filling loop is letting by or your plate heat exchanger has perforated and needs replaced