I am your typical Joe Public, I can read about gas boilers and systems etc and then ask the Gassaferegister listed person to come and look and give me a quote for the work required. It is ME that pays the bill.
Installer A looks at the gas feed pipe from meter to boiler-10m distance-with take off for gas hob, and says that the present 15mm copper pipe will not do because it won't carry enough gas pressure and will need a 22mm pipe.
Installer B looks at same pipe and says that the concrete rendering over the Victorian brickwork that uses the 15mm copper pipe as an edge/finish line, about 8 inches above ground level, will not do as rendering corrodes the copper and will not get signed off. Rendering has been there for 20 yrs.
A said nothing about this rendering and B said nothing about gas pressure.
This Joe Public is now confused by the comments/non-comments of two registered, qualified installers.
Are they both correct , but missed a bit or what !!!???
Think this is the best page to ask .