Radiator Not Heating Up?

Discussion in 'Plumbers' Talk' started by Dilligaf, Jul 11, 2023.

  1. Dilligaf

    Dilligaf Member

    I have had this problem for sometime now and people were helpful indeed on a previous post about this last year.

    I have an open system and 9 radiators in my house and one of them in the living room is proving to be difficult, I get heat at the TRV side but not the other and the whole rad is cold.

    I drained the system and put the mains hose pipe on the side that was cold to see if the pipe might be blocked inside the wall but it turned out to be fine as it was blowing water back up into the tank as well as removing the radiator and flushing it out.

    I have replaced most of the TRV's and Lock Shields and after bleeding all the air out and running up the gas boiler I closed off all valves except for the troublesome radiator but it was still the same. The pump seems fine yet this radiator still won't heat up. I am not sure about this micro bore pipe either, surely 15mm pipe to the radiators would be better!


    I have run out of ideas now and not sure what else I can try, any ideas anyone?
     
  2. HarryL1234

    HarryL1234 Screwfix Select

    If you've eliminated the radiator and the valves then it's the pipework. When you switch on the heating with just the living room radiator on, does the pump labour? BTW I would recommend having one other radiator on, in case the pipe is completely blocked to avoid overpressure in the system.
     
  3. Dilligaf

    Dilligaf Member

    I just tried it again and listened to the pump, doesn't sound like its labouring. I will keep in mind thanks about opening one other radiator. As I said about the pipe work on that radiator I attached the hose pipe from the mains and turned it on, the pipe was clear...??
     
  4. HarryL1234

    HarryL1234 Screwfix Select

    Could it be that both sides of the radiator are attached to the same pipe? In other words, it was incorrectly installed?
     
  5. Dilligaf

    Dilligaf Member

    Thanks but no, it used to work alright...
     
  6. HarryL1234

    HarryL1234 Screwfix Select

    A leak in your system?
     
  7. HarryL1234

    HarryL1234 Screwfix Select

    Also, it sounds like you checked the pipework on the return side but not on the feed side as the pump would have prevented water flow. Another question, did the radiator just stop working for no reason, or was this after some work or change to the system?
     
  8. Dilligaf

    Dilligaf Member

    Yes you’re right on the return side.
    On the TRV side it was hot so I figured that pipe was okay. Well it seemed to all of a sudden stop working at least a year ago but not due to any work.
    I can’t see any leaks anywhere, the walls aren’t damp or anything like that…
     
  9. terrymac

    terrymac Screwfix Select

    Take the rad off ,and let water flow out from each valve for several minutes .
    Have you replaced both valves on the problem radiator ?
     
  10. HarryL1234

    HarryL1234 Screwfix Select

    OK, maybe time for a quick summary of the problem as I see it.

    The symptom is a lack of flow of water through your radiator, as clearly evidenced by the fact that one side is hot and not the other.

    So, there is a blockage somewhere or a lack of pressure to drive water through your radiator.

    Your focus seems to have been to try to locate a blockage, which I agree is the most likely problem. You have eliminated the following as being blocked:
    1. The radiator
    2. The TRV
    3. The lock shield
    4. The pipework on the return side.

    This leaves the following possibilities for a blockage:
    1. The feed pipework
    2. The lock shield, if it's unidirectional and on the wrong side.

    If the problem is a lack of pressure, this could be down to:
    1. A leak (but it would have to be a substantial leak)
    2. Faulty installation (but you say the radiator was previously working)
    3. A weak pump, which may be generating enough pressure for other radiators but not the faulty one.

    I may be missing something here, but I can't see other possibilities.
     
  11. Dilligaf

    Dilligaf Member

    Okay I’ll try that and I do have to admit I didn’t replace the lock shield on the problem radiator but water was flowing when opened with it disconnected from the rad so it has to be okay right?
     
  12. Dilligaf

    Dilligaf Member

    Brilliant I like your summary and appreciate the time you and others have put into this thank you.
    I didn’t replace every single lock shield valve as they were working before and not leaking including the problem radiator. When disconnected from that rad the water flowed out of it freely so figured it was okay.
    I thought it was interesting about the pump being weak though. Is there a way of testing this?
     
  13. terrymac

    terrymac Screwfix Select

    How long did you allow water to run out of the lockshield valve ,it needs several minutes really.
    If the pump was weak ,when all other radiators were closed off you would get flow through the problem rad.
     
  14. Dilligaf

    Dilligaf Member

    Right so the pump should be okay then. I didn’t let the water run from the lock shield for long when off the radiator but as I said with the lock shield completely removed and the hose pipe attached to the return pipe it was flowing back into the tank…
     
  15. terrymac

    terrymac Screwfix Select

    Ok ,that's a good sign ,test the other valve . When flushing the radiator I assume the hose went into the TRV side ,and flowed freely out the lockshield side ,what type of radiator is it ?
    I suspect there is no flow through the TRV / it's pipework
     
  16. Dilligaf

    Dilligaf Member

    I flushed the radiator without the valves, I took it outside and did it.
    The TRV is new on the other side and it’s that side that gets hot.
    It just absolutely bizarre, I’ll have another go at it over the next few days…
     
    terrymac likes this.
  17. stevie22

    stevie22 Screwfix Select

    I had 1 rad that for years worked intermittently: had it off the wall and flushed a couple of times and all clear.

    Eventually found that some lazy plumber had just pushed one of the transit plugs in and that little plastic bit was acting as a random action valve.
     
    Dilligaf likes this.
  18. Dilligaf

    Dilligaf Member

    Okay just looked at the problem radiator again this morning and took off the TRV side from just the radiator and put the tank filling again and the water was running through the radiator fine, I let it run for about 10 minutes.
    I then closed the lock shield & with the TRV still disconnected from the radiator I opened that up and the water just dribbled out and stopped.
    This seems like it could be the problem with that line but why was it getting hot at that end of the radiator?
    What do I do now??
     
  19. terrymac

    terrymac Screwfix Select

    Are you telling us that a hose pipe connected to the TRV ,or its pipe, allows water to flow into the tank, but water does not then flow out from the TRV at full rate of flow ?
    If so ,there is a blockage in the pipeline.
     
  20. Dilligaf

    Dilligaf Member

    It’s the water from the tank is not coming out of the new TRV when opened.
    I assumed it was okay before as it was getting hit that side but obviously not.
    I am hoping to connect the mains hose pipe to that line and blast up through, what do you reckon?
     

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