Gas pipe size for condensing boiler

LondonBen

Any plumbers in the know please let me know what you think:

We have had 4 quotes for a new boiler. We currently have 15mm gas supply pipe which is buried in concrete floor. It feeds a gas hob and the boiler. We have no other gas appliances. 2 salesmen have said we will have to have pipe upgraded to 22mm gas feed or the warrenty on the new boiler will be void. 1 plumber didn't say anything at all about the pipe and when I pointed it out and asked he said he'd have to change it, and another plumber has said it will be fine and the warranty says about pressure of gas supply not pipe size and with the short run and only the hob the pressure will never be drawn down.
Obviously makes afair difference to the job if the pipe is left or changed.

Any advice?

djohn2002uk

You need 22mm to the boiler and you can tee off a 15mm to the hob.

robowen

djohn2002uk wrote:

You need 22mm to the boiler and you can tee off a 15mm to the hob.

Can't add much more to that !!

15mm will not be enough for the size of the boilers today. Check the manufacturers instructions of the boiler you plan to buy. It will tell you what the pipe size should be.

I'll bet me life savings on it being 22mm.

rob

moneysavingplumber

It may hold a decent working pressure at 15mm if it's only rated at, for example, 8KW (subject to testing of course), but it would be far better to have a new supply fitted anyway, if it's copper and unprotected in the screed or concrete it should be replaced. I fitted a Keston C40 that modulates up to 40KW a while back and fitted a 28mm gas supply over a distance of 3m, and the working pressure was still well below what it sould have been. Long story short, Transco had to replace the gas main (i.e. road dug up, mole up the side path of the house etc) as it was inadequate for the property, which still left the working pressure slightly short of the industry standard, but the manufacturers were satisfied and Transco were happy to recommission on that basis. Just goes to show that you should take the issue seriously.

LondonBen

Thanks for the replies. I did think it would need replacing in the first place, but the plumber I liked best (corgi registered) was the one saying it wasn't needed. I have now spoken to him again and he has agreed to replace it for £160 approx extra to the initial £400 labour cost.
Hard for me to say if this is good or bad, but it won't be going under the concrete. It will run along the wall above the skirting and be boxed or covered (i think). It will have to go through one internal wall.

The reason I have chosen him is because he lives very locally, and by my reckoning less likely to "do a cowboy job". He does seem nice as well.

robowen

A quick call to the manufacturers will tell you what the pipe size should be.

The manufacturers instructions are the bible. These instructions supercede any regulations by any other organisation.

I can honestly say...the last 20 or so boilers I've done have all required 22mm supply. I can't see yours being any different.

I'd be less inclined to use this bloke if he's got his pipe size wrong. :think:

rob