Question about pipe sizes....

16 Jun 2007
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United Kingdom

I have just purchased a house which has had its boiler removed and some of the radiators.

I am going to do the pipe work myself to keep costs down.

All the pipes are there ready to connect to the boiler, however the flow and return pipes for the heating are 28mm in size.

The 28mm pipe goes up to the first floor (approx 7 meters) and there it connects on to a 22mm pipe (2 meters) from this it T's off (22mm to 2x15mm reducer) going to 3 radiators and a towel heater all up starirs. also T's off from the 15mm pipe backdownastairs and into 3 more radiators.

I have 2 questions:

Am i going to have any problems connecting a 22mm pipe from the back of my Biasi 28k, 80,000btu boiler into the 28mm and then reduced down to 15mm for the rest of the house?

Would it be better to replace the 28 mm with 22 mm pipe and then run 2 or 3 radiators off that?

If that doesn't make sense i can draw a picture for you.

Any help would be appreciated cheers!!!

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28mm can handle 24kw now prob. 7meters! How high are your ceielings!

What pipe work are you doing yourself exactly if its already there?
The work i'm going to be doing myself is connecting the radiators on to the pipes, they have all been cut off, don't know why.. also the towel heater is going to be wall hung so i need to channell a pipe in the wall...

It's 7 meters because the boiler is going to be placed where the pipes are in the extension and the pipes go up into the bath room, across to the back bedroom where the first connection is, i'm toying with the idea of T'ing off in the bathroom and going to the towel radiator first then onto the bedroom as this uses less pipes than the current pipework, meaning it all gets hotter faster!.

I didn't know whether it would have any adverse effects going from 22mm from boiler to 28mm back to 22mm then to 15mm and on to 7 radiators. Is there more chance of leaks?

Oh yeah, ceilings ar a good 2 and a half meters, bathroom is 3 meters wide, and its about 1 and a half meter from extension to kitchen. so approx 7 meters to first connection!!
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You need to work out the outputs of all the rads together. Up to 60,000btu(18Kw) will be ok in 22mm, if greater than this start with 28mm off boiler tails. Only drop to 15mm if rad output <= 14,000 btu (3.5Kw approx)
cheers Gas4you.

my boiler flow and return is in 22mm, will this be ok going into the existing 28mm then back to 22mm, or am i better off ripping out the 28mm and just using 22mm and then feeding off to the rads in 15?

Its no problem using a larger pipe size.

What is a problem is feeding more than about three rads from a 15 mm source !!!

One also wonders who is going to install and commission the boiler and why they cannot advise you on the pipe sizes for heating.

I'm gonna get my corgi registered plmber to install the boiler and comission it.

I just wanted to get all the pipework done and ready so that he only has to connect the gas and make sure its not gonna explode.....

I had some quotes from about 4 plumbers and they all said about the £3000 mark to do eveerythin.... however i managed to get all my pipes and boiler for less than £500.... wasn't prepared to pay out £2500 in labour charges!!!!

I've had a quote for installing the boiler and connecting gas at £300.... which is definatley a lot cheaper for me.....

Moneys very tight at the min as every room in the house needs to be gutted and started from scratch!!!!

Soldering a few pipes myself isn't particularly dificult and it also means I can get it all done faster as none of the plumbers i spoke to had time to even start in the next fortnight!!!!
The minimum the CORGI has to do is fit the mounting bracket, assemble and fit the flue, run and connect the gas supply and commission the boiler and notify the installation to CORGI/Building Control.

In London we are likely to charge about £180 for that based on two visits.

£180, thats good to know, i'll shop around a bit more i think....

Thanks for everybodies help...


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