I have a Vaillant combi boiler that I have had since new. A problem has now developed. Whenever I flush the upstairs toilet the boiler turns out with error code f22. The puzzling thing is that this only happens if the upstairs hot water tap is running. To avoid the boiler turning out I can turn the hot water tap off, flush the toilet and turn the hot water tap back on!

Navdeep, August 2007

New PCB it's all that will work

iscer, May 2009

.....Oh & this happens even though the water pressure is reading almost 1.5 bar.

Navdeep, August 2007