10mm or 15mm tube for CH?

[Lobster]

I'n currently refurbishing the living room, which will include replacing the knackered old radiator.

The rad has underperformed ever since we've been in the house (18 years ago); it was originally plumbed with 10mm copper tube and not long after we moved in, while we were having an extension built I had it changed to 15mm in the misguided belief that it would help. It didn't. I think it's probably a poor, under-specced and probably clogged radiator.

Anyway, so I'm now replacing the rad itself, and will obviously ensure I get one properly specced for the room and will take it from there. My question relates to the pipework... currently we have a pair of 15mm pipes emerging from the ceiling and running round the room, and I'm considering reinstating 10mm to be less conspicuous. Whether that's actually worthwhile from a cosmetic viewpoint is debatable, I know, but is there any other reason not to use 10mm? Is it actually likely to significantly restrict flow? The relevant section (ie from just above the ceiling) would be about

5m each way to the rad.

[www.GymRatZ.co.uk]

Knowing how much I have to throttle back a number of my radiators to get any temp drop across them I can't see it making any difference.

Might actually be quieter then turning the L/S valve to "only just open" on 15mm feed

[Tricky Dicky]

I originally had a microbore system at the last house, the only problem was domestic management constantly ramming the vacuum cleaner against the pipe s either compressing them or bending them along with twisting the valves. T his caused numerous leaks over the years and was only solved by going up to 15mm as radiators were replaced. One other aspect of microbore is it very difficult to make the pipe work look neat running on wall surfaces unless y ou run it in the wall or in trunking/pipe boxing.

Richard

[RobertL]

I was told to use 10mm only for one radiator. If the pipe was feeding 2 rads you needed 15mm. The limit is, AFAIK, not because of the pressure drop but the flow noise.

one thing i found out the hard way was not to use 10mm compression fittings (which always seemed to leak) but to solder a 10-15mm adapter onto the 10mm tube and then use a (15mm) compression fitting.

[Tim Watts]

Wondering if that is because the 10mm tube is fully annealed?

[Malcolm Race]

Living in a 15YO Redrow house I have a problem with a rad in the lounge. It takes longer than the rest to heat up in the morning. The system is 10mm microbore with the pipes from manifolds under the first floor with the pipework run between the blockwork and dot'n'dab. The problem surfaced about 5 yrs ago and my heating engineer (who lives in a similar house on the same estate) suggests that the problem is crud in the pipes where elbows (rather than swept bends) are used to change the direction of the flow. The system has been cleaned with little effect so that all I can do is wait for redec and replace the elbows.

If you use 10mm, use bends wherever possible rather than Tees

Malcolm

[RJH]

I recently took a run of 10mm flexible plastic pipe from 15mm copper. The inserts dropped the internal diameter to 5-6mm at joints. Seems to make no difference to the rate at which the rad heats up, or temperature.

Brilliant stuff, btw, 10mm plastic. Very easy to work with, and fed behind the radiators/through the wall under the floor, so no exposed pipe.

Well, I say brilliant. time will tell ;-)

[meow2222]

microbore has lower power limits, and is more vulnerable to clogging. What power output does it need?

NT

[Michael Chare]

I was looking at some 10mm copper pipe in someone else's house and I thought that whoever installed that has the same problem as I do. The pipe comes in rolls and it is then very difficult to get it dead straight.

If its the living room I would have thought you would need more rather than less heat which might be difficult to provide if the rest of the system uses 15mm or larger pipes. The length of the pipe run to the radiator will also be a factor.

[bert]

In message , Lobster writes

All my downstairs rads run ok and IIRC it's 8mm