On Wed, 24 Nov 2004 10:11:34 +0000, bilge wrote:

I have been told that the 15 mm gas supply pipe to my 8 year old
Vaillant TurboMax vuw 242E should be 20 mm .

Is this correct?

No, it should (almost certainly) be 22mm .

The installation manual only states a minimum of 15 mm.
And the minimum is presumably not good enough here.
See FAQ.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html