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Our 15yr old boiler has packed up and I am getting quotes for a new Valliant and Worster Bosch. The pipe work coming out of the gas meter downstairs is 22mm but it looks as though is it only 15mm by the time it reaches the boiler(upstairs, 6m over). I have only been able to trace it upstairs part way where it is still 22mm but not too close to boiler.
The issue is that different people quoting have said different things about this pipe.
One fitter said if fitting a valliant i don't need to get the pipes changed but i would for the Worcester(due to connectors they have) and as the wider pipe goes through much of the house it would be fine to leave- just slightly lower efficency. The other fitters have said it MUST all be 22mm to do by the book. Typically the cheapest was the one that didn't think the alterations need doing.
I'm so confused- please help!

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This is the first time I have ever replied to anyone on a forum so I hope this works.
The pipework size depends on the kw rating of the proposed boiler and the distance from the meter and also on the number of bends and tees in the pipework and if there are any other gas appliances in the property.

If it is a combi boiler the pipework will definately have to be 22mm normally write up to the appliance, to cope with the hot water demand hope this helps.

Gas fitters i've worked with have always used 22mm - i think that the cact that the boiler has a 22mm connection built into its manifold is a hint at what is expected.

Thanks for your help- just had another quote today saying it should be changed so the overwhelming opinion seems to be that my bargain boiler man is happy to cut corners :(