How can I top up the water level in my Vaillant Combi Boiler?
I have a Vaillant Combi Boiler of about 2 or 3 years of age, I have lost the manual and cant seem to download it from Vaillant website. I want to top up the water level as it is below 0.8 bar but am not sure how to top it up.
PAUL, September 2008