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ive got a 20 year old heating system with a glow worm boiler running 8 rads through 8mm micropipe,recently the upstairs rads were hot but downstairs cold,had boiler serviced and new pump but no joy.i managed to get them all working now by turning the upstairs rads down.been reccommended a new system installed with new boiler and repipe to 15mm,dont mind replacing boiler but dont want to repipe because house has just been refurbished and dont want the mess.will a new boiler be ok on the origanel 8mm pipe ,maybe if system was powerflushed to allow all rad valves to be fully open and effective?

Frankly, I hate microbore and 8mm is the worst of all. I suppose a new boiler would work without any changes, but that would still leave the problems of a system that cannot be balanced properly.

It may be that the increased output from a new boiler cannot be dissipated properly which may reduce efficiency but ultimately, the decision whether to upgrade the pipework is yours.

every heating engineer ive spoke to shares your dislike of 8mm microbore,when the upstairs rads are turned off downstairs are red hot,does this indicate that the system water is finding the easiest route and the pipework could be sludged or furred up ,if so are there any diy alternatives to poweflushing.can anyone reccommend why my system wont balence out properly

ive recently had a downstairs radiator taken off and pipes left on closed valves ready to take into new conservatory ,could this be contributing to the above post problem?

any advice would be much appreciated

If you're having problems getting the system balanced, and a new pump has been fitted, it's possible the flow of water has became restricted. 8mm minibore is prone to becoming blocked, the best solution is to re-pipe.

Removing radiators and flushing with a hose or pressure washer can improve the flow of water, powerflushing 8mm pipe is very a rarely a total success because of the resistance of the 8mm pipe.

Hope this helps

My sister had similar problem. We would get it running then week later stopped again. In the summer I fitted TRV's to all radiators this cured the problem. I guess as each room gets hot it switches off and pushes it through any radiators not turned off.

Recently had similar problem, problem was cured by re-piping with 15mm to nearest point where piping entered room thus leaving 8mm tails to rads causing least disruption to decoration of house.
Hope this helps

many thanks for the advice,ill try fitting trv's to rads,sounds like a good cost effective idea .will post result to anyone interested.thanks again to all users who answered my post

There are many people like me who have 8mm pipe where it is appropriate.
If you live in a soft water area, or you take the trouble to read the manufacturers instructions and fill with de-ionized water there is no problem.
Likewise, setting up the system so the water goes where you want it to, is no more difficult, than any other system.
However, as with any other system, the pipe size, length and heat loss needs to be taken into account, as does the pumps ability to deliver enough water through the system to make it all work.
From what is written, the system has worked perfectly well for years, so what has changed? Nothing I would guess that requires such drastic action.