Central heating flushing - cold pipes

Discussion in 'Plumbers' Talk' started by jdtheo, Dec 15, 2012.

  1. jdtheo

    jdtheo New Member

    Hi,

    I have a tradional open central heating system which I believe is blocked somewhere in the pipework as the two radiators downstairs are not getting very hot. On both radiators one of the pipes (i believe the input) is warm at best.
    I know when replacing my metal FTE box last year that there was a lot of sludge in the system.
    I took both radiators off the wall approx a year ago and cleaned them out so dont think its blocked rads.
    The valve which has the drain cannot be turned off so it looks as though I will have to drain the system.

    I cannot afford the £400 for a Power Flush, but have read reports about just using the mains supply to try and blow back any crud in the pipes. I intend to remove the last radiators (one with drain) and connect an input and output on each side of the piping.
    I have a few questions, that I'd really appreciate answers:

    I know my option is not as good as a Power Flush but does it have potnetial to clear a blockage?
    Do I have to block the supply and vent in the FTE tank?
    Do I need to put the motorised valve into open position?
    Do I have to do anything specifically with the boiler (other than turn it off!).

    BTW, I have tried X800 etc to no avail.

    Many thanks.
     
  2. hibeealex

    hibeealex Member

    The most common place for a blockage on your system is where the feed tee's into the heating pipe work which should be before the pump somewhere get a small magnet and run it along the pipework in that area and see if you can find any attraction, if you do cut that section of pipe work out and replace it. if you flush then yes the motorised valve will need to be open
     
  3. jdtheo

    jdtheo New Member

    Thanks for the advice hibeealex. This was the case last year when the piece of pipe totally blocked and I had to cut out that section. But it seems clear now. The upstairs rads are fine, it's just downstairs.
     
  4. hibeealex

    hibeealex Member

    Have you tried closing the upstairs? see what happens to the downstairs then in case its just a balancing problem
     
  5. Crowsfoot

    Crowsfoot Screwfix Select

         Hi jdtheoy,
         For a quick fix I'd change the pump it's probally flagging if it's been in a few years.
       
    Flushing radiators whilst in position with a powerflush machine or giving it a mains flush as a very high potential to go wrong so I'd wait for the winter to end then take each radiator off one by one and individually flush them outside with your hose pipe.
    Add some new valves as well, but not TRVs (they are rubbish).
    Tappy,
     
  6. tom.plum

    tom.plum Screwfix Select

    in my experiance if a pipe has got so blocked that the several rads won't work, a flush will not shift it, it blocks usually on a tee to a unused part of the system, where a rad or section has been blanked off and the tee's not removed, its a gradual blockage where the pipe reduces in size untill there's only a slight hole for the water to pass,
    here's one I cut out a while ago
    *

    Message was edited by: Screwfix Moderator
     
  7. itchyspanner

    itchyspanner Member

    no flush will remove a bad blockage. you need to find and deal with the blockage, if its microbore it could be a crushed pipe? a foot pump can sometimes move blockages if your lucky. once you have circulaton get a powerflush done as you seem to have alot of sludge in the system . Mains flush dont cut it, rads off and flushed with hose is good but still not as effective as a powerflush. anybody who says different does not or has not powerflushed correctly. If the system design is causing air to enter it should really be redesigned to help stop the problem.
     
  8. petertheplumber

    petertheplumber New Member

    Lets also remember that it is worth finding out why there is so much sludge, does a rad get bled regularly? have rads been taken off and put on a lot. If bleeding has been done a lot then the air vent is in the wrong place. If you try mains water the vent and cold feed in the loft need to be closed off with isolating valves, and the isolating valves on the boiler should be closed or the pipe disconnected from boiler. Find the blocked section and treat that seperately exposing both ends. and the motorised valve needs to be open to CH
     
  9. tom.plum

    tom.plum Screwfix Select

    peter, get a drink and chill, are you a vicar by any chance?
     

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