Vaillant Boiler Noisy when lights

Butterfliesarepretty

I have had my vaillant boiler since I moved in six years ago so it is about 9 years old now. Its been brilliant combi boiler, one thing went wrong - a stuck valve. I got it replaced two years ago.:T

One thing that always happens with my boiler is that when it comes on first time, it lights and makes a loud bang as if someone is hitting it. Radiators work very well, all bled, and pressure of water is 1.5 - 2. I have not had it serviced for three years (can't afford it yet) but it works great.

does anyone know why it makes a bang noise first time it comes on??

vikingaero

I have this problem on my Potterton. The safety value sometimes "bangs on and off. Once or twice the valve has opened and spewed water out everywhere. It seems to be a problem on modern boilers where the tolerances are finer and the boiler gets blocked with sludge. As my boiler is 15 years old I'm putting up with it and biting the bullet next year for a new boiler and a powerflush.