Cold feed blocked - how much pipe to cut?

Discussion in 'Plumbing and Central Heating' started by dmjones500, 15 Oct 2016.

  1. dmjones500

    dmjones500

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    Hi,

    Today I drained my open vented heating system to change a leaking radiator valve. The system appears to have fully drained - all radiator valves are opened upstairs and downstairs, and the draining water has stopped.

    The header tank is still full. Research suggests this means my cold feed is blocked somewhere. Using a magnet, I found evidence of metallic buildup in the tee between the cold and hot feeds (which I believe is the standard place to find it!). This is shown in my picture, circled in red.

    [​IMG]

    The suggested remedy is to cut out the pipe section and replace it. However, since my floor is kinda close to the tee and so is the pump, I'm not sure how much pipe I can/should cut out.

    I'm thinking I'll disconnect the pump from the tee (seems to be a screwed joint), then cut fairly close to the tee at each side and replace it/clean it, then reconnect using compression joints.

    Is there anything else I should check/try before I go ahead and do this?

    Thanks, Duncan.
     
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  3. ajstoneservices

    ajstoneservices

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    Cut the pipe about 150mm above the tee, drop the pump out and use a long screwdriver or something similar to clear the blockage.

    Bung the outlet on the f&e first though.
     
  4. dmjones500

    dmjones500

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    Thanks for the reply. Just to check I understand, am I cutting the pipe once above the tee? If so, do I just bend it a bit to get access with the screwdriver?

    Also, does "drop the pump out" mean to unscrew it from the tee? Or do I unscrew the pump at both ends and get it out the way?

    And finally, do I just need one compression joint to reconnect the cut pipe again?
     
  5. ajstoneservices

    ajstoneservices

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    One cut above the tee and move the pipe out of the way so you can poke something down the pipe to clear it.

    Remove the pump so you can get access to the blockage.

    You can use a compression coupling. You will need to clean the paint off. That's best done before you cut the pipe.

    You will have drained down before you attempt this won't you.
     
  6. dmjones500

    dmjones500

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    What I've done so far is to drain the heating system, opened all the rad valves and also the air valve you can see in the top-left of my picture. I'll either mop out or bung the f&e tank before I do anything. Is there anything else I can do to drain things before I begin? I'm assuming there's a small unavoidable bit of water coming in my direction as soon as I cut the pipe...
     
  7. ajstoneservices

    ajstoneservices

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    You have found a drain cock at low level somewhere and attached one end of a hose to it and taken the other to a suitable place outside. Tehn opened the cock? That's how a system is drained.

    You will get whatever water is left above the blockage come as you cut that pipe.
     
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  8. dmjones500

    dmjones500

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    OK, good. Yes, I've drained it already in the manner you suggest. Thanks for your help, I'll give the pipe cutting a go...
     
  9. Steelmasons

    Steelmasons

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    I doubt any blockage will be on that tee.
    Where does the cold feed enter system??.possibly tees into open vent pipe in loft..
     
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  11. Stadan20

    Stadan20

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    +1 what steel says
     
  12. dmjones500

    dmjones500

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    The cold feed enters via a tee, slightly higher up. There is no magnetic material that I can detect at that joint. Photo below (15mm pipe is the feed coming from the f&e, 22mm is the vent.

    [​IMG]

    Is there any way to figure out if the blockage is there without cutting?
     
  13. Stadan20

    Stadan20

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    I would confidently say it's blocked there
     
  14. ajstoneservices

    ajstoneservices

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    I thought it was combined vent and feed. No matter worst way you'll have two cuts. 1 above the pump and one at the 15mm pipe. If you cut above the pump you can clear up and down and if needs be then cut the 15mm and clear the branch of that tee.
     
  15. Stadan20

    Stadan20

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    I would suggest to bung the f and e outlet before doing so though
     
  16. dmjones500

    dmjones500

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    Thanks folks. So I will cut below the 15mm/22mm tee, allowing me to clear up and down the 22m pipe. If that isn't where the problem is, I'll cut the 15mm and tackle the problem from there.

    Stupid question, but can I use a push fit coupling to join a pipe I've sliced? Would I be able to force the pipes about enough to get the fitting in place? Or should I be going for a compression fitting?
     
  17. Stadan20

    Stadan20

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    You may struggle to get compression on that tee piece next to the pump . Other connections should be fine
     
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