Fitted my first and last vaillant last week, nothing is screwed (except the flue, which is worrying as you have to make 3 connections compared to wb's 1 connection.) pipe didn't go behind so all pipe work visible. The start up process takes forever, purging and testing etc. the valves are rubbish, prv was impossible to connect when flow and return connected. Condensate is glued on to connection in boiler. Condensate must be put into a w.machine trap to prevent syphonage. Absolutely cack, customer was alimentary so I fitted the piece of cack, never again!! Lost a job last week as another plumber recommended a glow worm with 10 year guarantee, so looking for alternative to Wb.
Funny that, I find Worcesters a nightmare to fit. Are the templates still made of tissue paper?