most of the services have been done by the installers. They couldn't fit me in one year when I wanted so I had a vaillant installer off the web site do it and they didn't change burner seal,its due this April I will tell next service ebg to replace it. What do Vaillant charge for a service ?
How old was the boiler when the web engineer came?
As stated its only recommended to change it every 3-5 years.
I have to say that although I don't get called to service that many Vaillants probably over 50% that I see at about 6-7 years have never had the seal replaced which means never properly serviced ( if at all ).
Tony