15mm for central heating?

[karenmorgan]

Can/should you use 15mm copper for central heating? I never have but then I havn't been plumbing for long.

 

[tamz]

You should size the pipes to suit the load on the system. On domestic systems 22mm or 28mm (depending on the load) from the boiler, teeing of and reducing as you go around the system.
These days it is generally considered to be best practice to pipe the rads in 15mm. This is more for aesthetic reasons and to help the hard of thinking rather than it needs to be as it will work well with 8 and 10mm just the same if a bit thought is put on how it is piped.

 

[karenmorgan]

I have always piped with 10 but I worked with someone else yesterday who piped everywhere in 15mm ( small size 4 bed house) The new rads we fitted were longer than the old so he put elbows on the existing pipes and ran the 15mm to the valves. I thought it looked awful but then what do I know!!!!!

 

[tamz]

It probably did look awful.

10mm will do most domestic rads no problem.

 

[Nat]

As a rule of thumb 15mm is ok for 3 rads max. If there are mote than 3 I use 22mm until I have 3 or fewer to run to. Either that or run 22 to a manifold then run 10mm to each of the rads from there.

 

[Best]

And if you really wanted to use 10 mm pipe, from a manifold or direct from a 22 mm pipe, you have to make sure not to do long runs, as they can't carry a lot of flow. Remember, as has been said in other posts, that each rad has flow & return, so even a short combined run to a radiator could be 8 or 10 metres! I prefer 15 mm to rads but 10 mm will work if you are careful to do each pipe on short run.

 

[jase158]

I was wondering similar, with newer boilers I have seen, whole system run in 15mm pipe from just above boiler to all rads.
It all worked (with a bit of balancing) but what are the chances of it going wrong later?

 

[stevetheplumber]

10 mm will feed most rads im most domestic situations weve run as much as 10metres from a manifold in 10mm with no problems

 

[stevetheplumber]

I was wondering similar, with newer boilers I have seen, whole system run in 15mm pipe from just above boiler to all rads.
It all worked (with a bit of balancing) but what are the chances of it going wrong later?

if it works when you fit it it will work for ever if nothing changes generally we work on up to three average rads on 15mmbut we always run 22m to the first rad before reducing or teeing of so in a small house with 3 smallrads upstair and three small rads upstairs we run 22 to the first downstairs rad but could tee of in 15 for upstairs before that but if the feed for upstairs was past first rad we carry the 22 up to that tee
ive seen plenty of 7 rad systems working perfectly well that are in 15mm entirely but for the sake ofthe price difference in a couple of lengths of 22 why risk it ?

 

[karenmorgan]

It probably did look awful.

10mm will do most domestic rads no problem.

Existing rads had 15mm pipes. It looked fine when all the old rads were in as the pipes came straight up through the floor to the right place. When you replace the rads with smaller or bigger ones, I think it looks terrible. Personally I would have preferred to run the pipes behind the rads and then bring them out in the right position. Or run all the pipes under the floor! Would this have been an option?

 

[jase158]

Existing rads had 15mm pipes. It looked fine when all the old rads were in as the pipes came straight up through the floor to the right place. When you replace the rads with smaller or bigger ones, I think it looks terrible. Personally I would have preferred to run the pipes behind the rads and then bring them out in the right position. Or run all the pipes under the floor! Would this have been an option?

was it concrete floor?
Always better to hide it, I wonder why sometimes as they paint pipework any way.
Had a customer who didnt want to see any pipework as they thought it was ugly, toilet, sink, radiator, all hidden.

A lot of the time down to cost too as you have to cover pipes when plastering or replace a few plasterboards, i.e.

 

[Best]

Existing rads had 15mm pipes. It looked fine when all the old rads were in as the pipes came straight up through the floor to the right place. When you replace the rads with smaller or bigger ones, I think it looks terrible. Personally I would have preferred to run the pipes behind the rads and then bring them out in the right position. Or run all the pipes under the floor! Would this have been an option?

Always best looking job to repipe from below floor, but if nice new carpet or wood floors, then you maybe can't. I think if new rad slightly wider you can put soldered elbows as high as poss & looks good. If new rad is slightly smaller & pipes are same distance out from wall, then chrome male sts & chrome pipe will join to rad valves. This looks ok & if it's hidden behind curtains, who cares?

 

[marleyco]

The plumber probably should have used extension pieces for a neat job or as I have done, bit of chrome pipe and fittings.

 

[tamz]

run all the pipes under the floor! Would this have been an option?

Always better to alter the pipes below the floor but this is not always possible.