Is 10mm plastic pipe OK

[dolph]

Renovating my kids’ flat, with several structural changes that will mean changes to radiators positions plus additional towel rails. The very old system pipes are basically scrap and I would like to put in 10mm plastic pipes that could be hidden, running these from a central manifold, 22mm inlet, thereby all joints would be above floor level.

Having utilised 4 radiator calculator sites (why do they differ so much} the figures are as below. I propose to use in the four main rooms exactly the same radiator of 3700 BTU’s, with TRV’s and a thermostat programmer in the Reception (as it is the biggest room with the highest temperature needed, the others would turn off first?). The distances from the manifold to radiators is shown, can I use 10mm plastic to supply the radiators

Sorry I have spent over an hour to produce a table here but it wont take it forward. So shown next to each room are;


Average BTU ; Highest BTU; Distance in metres from Manifold to Radiator



Kitchen 2166 3272 5.5

Reception 2836 3555 6.5

Bedroom Front 2765 3153 4.5

Bedroom Back 2699 3016 6.0

Bathroom (2) 656 792 1.5

Hallway 390 427 3.5

Total BTU 12267 15007

Total Watts 3593 4398

Whilst the distance to the hallway is shown as 3.5 metres this is from kitchen radiator, could I ignore the manifold in this case as the hallway radiator will be only 1.6 metres from the 22mm flow and return pipes, could I tee off these?

 

[DP]

I would keep the existing copper and alter it to suit.
Hate plastic, I know it is here to stay, but does not mean I have to like it.
Having said that, I have a customer who has 10mm plastic to some radiators. Some of these pipes are now blocked, will need replacing. No circulation through plastic but copper 15mm ok.

 

[dolph]

Unfortunately some of the copper pipe is above the skirting board, has had about 6 coats of cracked paint when above floor, some of the joints have green/white "powder" round them, the remainder is buried in concrete with no covering as far as I can see. It was fitted in 1976 and only operates to the central heating, very slowly, electric immersion cylinder heating only! The place is being completely renovated and the boiler being moved from the back of the flat to the front so the piping is of little use anyway.


My idea with the plastic is the ability to create a brand new system with no joints hidden and 10mm will enable me to hide the pipes behind skirting boards or in wall channels. Would 22mm plastic pipe fur up dramatically so quickly, as properly fitted surely would mean very little change of water within the system would occur year on year especially as this is what Fernox etc is supposed to prevent.

My reason for my question is more about the distance of runs of the pipes from manifold to the rads maximum 6 metres at the longest, would 10mm pipe be big enough to supply the rads. I read somewhere rads under 8000 BTU's can be supplied by 10mm, all mine will be less than half of this level.