Micro bore

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  • Micro bore
  • muddyjames

    So I’ve a microbore plumbing solution at the moment for my radiators. They’re pressed without convectors and with single entry connections. Whilst this seems a brilliantly tidy system, no one seems to think so anymore.

    So I’d like to swap the rads for convectors and pressurise the circuit but every plumber that’s been round says they don’t want to reuse the existing pipe work.

    I’m wondering has anyone gone down this route and subsequently had a blockage or had to deal with a problem like a leak under the screed.

    I thought this was going to be about Noel Edmonds.

    I have microbore plumbing on heating. We had the boiler changed for a combi a few years ago including a power flush of the system. No problems. Plumber said people are just trying to charge for a complete replumb.

    Premier Icon matt_outandabout

    We had two plumbers refuse to install new boiler because of it in our house.
    Third just said ‘it’s not ideal’.
    I’ve re-routed much of ours to add thermostatic valves and added two extra spurs from the main manifold. Thankfully our manifold is under a hatch in the downstairs cupboard, so easy to access.
    It’s taken a bit to balance the system. I’ve three last radiators upstairs to replace and new TRV’s install this spring and I’m sure they will mess with the balance again….

    Premier Icon supersessions9-2

    Microbore is supposedly self balancing or so I thought. IANAP.

    I have a mixture of microbore and standard 15mm and a few column rads and have no problems with my heating. Had a few plumbers work on things in the past and never had any have any concerns.

    Premier Icon fettlin

    Combination of micro bore and 15mm here on a combi (pumped system).

    No big issues but they can be a pig to bleed properly. Have to force bleed some rads if I drain the system down for anything but other than that she’s champion.

    Not my first choice, I ripped all of ours out but it was a state, crushed in plenty of places and noisy as hell.

    No reason you couldn’t reuse it but you would be best getting a proper flush to get all the magnetite out and a filter installed.


    Those with combi upgrades presumably you originally had a vented system and then pressurised it?

    When you say re routed presumably that’s because there’s no longer a nice neat single entry option available that Has a trv.

    Re the balancing I do seem to get rads hot upstairs but down a bit Luke warm, I thought it might be air but maybe it’s balance.


    Ours isn’t noisy (quieter than the 15mm in our old house in fact which banged and creaked and generally made a racket). From what I can see the pipes look largely ok.

    Presumably if there was a lot of sludge I’d get black water when bleeding a rad? Or not necessarily

    We went from open-vented system to combi with no problem. 22mm main flow and return running the length of the attic with 8mm off to each radiator. We didn’t have those daft single radiator valves – they are bobbins. Did have a magnetic filter installed and a powerflush at the same time.

    Can’t see any reason why new boiler and better rads would be a problem, although new system throughout would be better. Depending on size of house and ease of access under floors it shouldn’t be that much more work.

    Source: am heating engineer.


    Thanks TFO. Assume yours is copper rather than the new er plastic micro bore. Down stairs we’ve a screed, so access to pipes is non existent other than the bit poking out of the floor. I Can see the downstairs manifold, not sure where the upstairs one is but expect it should not be too far from the airing cupboard in the middle of the house.

    They manifold looks like it’s just stuck on the end of a piece of 22mm pipe sticking out of the floor but assume there must be a couple of pipes within it to give flow and return.

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