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Discuss Suspect blocked rad pipe - can I do this workaround? in the Plumbing Forum area at

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  1. TheJames

    TheJames New Member

    Hi all,

    The rad in my parents kitchen gets lukewarm at best. I've had it off the wall and confirmed it's clean and not blocked inside. I've fitted new valves. The flow pipe does get hot, but even 6 inches away from the flow pipe the rad has a massive drop in temperature.

    My best guess is that there is a blockage in either the flow or return to that rad, allowing just enough water to pass to heat the pipe and make the radiator lukewarm. My plan to fix this is as follows, and I'm hoping someone can tell me if this will work (I'm no plumber, just reasonably handy).

    First, diagnosis.
    1. Drain the system
    2. Open up the lockshield, stick a flexible hose on it and start to refill the system. If the blockage is on the return then flow will be negligable. If flow is good, onto step 3
    3. Repeat step 2 but for the flow pipe. I'll assume flow will be crap if it was good for the return pipe.

    Cure - Option 1 (I hope)
    See if there is an obvious way to unblock the pipe. I doubt it, tiled floor and I can't see how to get access

    Cure - Option 2 (and where I need help)
    The rad is mounted on a partition wall that is shared with the utility room. The utility room has a small rad that works perfectly. Once I figure out whether it's the flow or return, can I just chop the appropriate pipe from the working rad in two, stick in a T, then plumb that into the right part of the non working rad. It would effectively mean two radiators sharing either a flow or return, but the working rad in the utility room can be switched off at all times.

    I think that works, but hoping someone cal tell me what I'm missing.

  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Yep agree with you for diagnosing

    As for fixing it I would say you have two paths

    You might be able to get a piece of wire and see if there's a blockage close to the rad and give it a poke (with the hose pipe attached) and see if you can clear it that way

    Or as you say repipe it depends what the other rad is piped up in 15mm your ok 10mm is a no go

    Hope this helps
  3. Harvest Fields

    Harvest Fields S. Mod Trusted Plumber GSR Top Contributor!!

    Have you tried putting the heating on full and turning all the other radiators off apart from the one that is not getting hot.
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  4. TheJames

    TheJames New Member

    No I haven't, best I did was turn off the ones downstairs. I'll give that a whirl before I try anything else.

    Shaun, thanks for the wire suggestion, I'll give that a go. I did see a clip on youtube where some guy was using a car foot pump to blow out a blockage. Is that standard practice? I was a bit wary of putting too much pressure in the system and causing a leak under the floor boards (oh I'd love that...)
  5. Harvest Fields

    Harvest Fields S. Mod Trusted Plumber GSR Top Contributor!!

    If it gets hot. Leave it running for a few hours then turn each rad on slowly one at a time until the heat comes through then move onto the next one until they are all on.
  6. JCplumb

    JCplumb Plumber

    Just close the valves, take the rad off then open the valves into a bucket. You'll soon see if one of them is blocked.
    If one valve only trickles out that's your blocked pipe. Often opening the valve into a bucket or hose pipe and topping up the boiler to say 2 bar will see your plug of gunk shoot out of the valve leaving a clear pipe behind.
  7. king of pipes

    king of pipes Trusted Plumber GSR

    A chemical clean of the system would probably dissolve any blockages your method of diagnosis is fine. I would tie up the ballvalve in the expansion tank drain the system clean out the tank add sentinal x 400 via the header tank untie the ball valve fill and vent the system , fire up the boiler and run the system for a normally for a week for and short period of time turn the rads off that do get hot and let the water push through the part blocked pipework to the lukewarm warm one this should dissolve any blockage , drain a flush the system ,refill as before adding x100 inhibitor . Sorted cheers kop.
  8. DuncanM

    DuncanM Plumber GSR

    Might be kinked microbore?
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