Heating in 15mm



I have just bought a house where a lot of the copper piping was ripped out while it was on the market.

So i need to put in most of the central heating pipes again and a new combi.

Now it looks like eaga had done the instal and it was done in 15mm copper. The boiler fed 3 rads upstairs and 3 rads downstairs.

I intend on using 22mm and add another 2 rads on to the system.

Could i get away with 15mm ? I also plan on using plastic and not copper for the piping.
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12 Apr 2010
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United Kingdom
Should be fine just make sure the extra rads and boiler are sized correctly, also Providing the main flow and return pipes are in 22mm.


I have now been told 15mm is fine and you only need to do 22mm for the first 2m from the boiler.

I am a bit confused as i am about to buy all my piping and was planning on doing 22mm for all the flow and return up to about the last 1m and then go down to 15mm. The reason being is i am doing it all in plastic and it is pretty cheap once you get all the coil etc to just use it up.

So i wonder if i should go for doing the system in 15mm and just use 22mm for the first 2m's ?

Any comments
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Use as much 22mm as you can get in and just use 15mm for drops to rads. Copper would be better for whole install but if your using plastic first metre at least on boiler flow and return must be in copper.

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