Hi, Just had a new Veissman fitted, 10 days ago.100-w.Installer, registered Veismann, said my 22mm pipe was ok, 0.8mlbar drop from meter to boiler. Had teething trouble, so Veissman engineer just left and said my boiler is operting 10% less due to 22mm pipe, needs upgrading to 25mm as much as possible.Underfloor run approx 15 metres, access by a hatch, but tapers, so a bit of scrawling necsessary.gas rate or burner pressure or combustion reading 9.2%co or 9.2degrees nco. cannot read his writing.inlet working pressure 19.9mbar.I am confused at why installer didn,t mention pipe upgrade, we did discuss posibility, but not cost, said I was ok.10% means my 30 kw boiler is only a 20 kw now.Any advice on whether the pipework upgrade is nescessary and a rough cost would be appreciated. Methinks the installer just wanted a straight change, as I did, no scrawling under floors.To add to things, Veisman engineer put f4 fault down as electrode change .never had a f4 fault, and he didn,t change any electrode, he was only here 15 mins.Had to justify his call out I presume, Not by me, but by the Installer.Bit confused.