No hot water fron cylinder

Discussion in 'Plumbers' Talk' started by Steveb2006, Oct 6, 2020.

  1. Steveb2006

    Steveb2006 New Member


    We have a fairly old heating system - a vented indirect system with boiler, hot water cyclinder and header tank in loft (plus smaller header tank for central heating / boiler water).

    Problem is we are no longer getting any hot water from the cyclinder. The central heating works ok - and we can get hot water via the immersion heater in the cyclinder.

    The boiler works ok. There appears to be no diverter valve in the system as far as I can see.

    With the hot water set on at the controls the boiler fires up and the main pipe out of the boiler gets hot but a foot or so further along the pipe (on its way up to the cylinder) it stays cool.

    I am trying to find the likely cause and most economical solution. It sounds like a blockage somewhere in the pipe system into the cylinder. New cylinder? Is it possible to get the system flushed?.

    We've lived with it for a while (hot water via immersion heater) but are thinking of selling the house so would be good to get sorted.

    Note that when we've had the boiler serviced the plumber has had a quick look at it and suggested possibly changing the cold water feed pipe to the cylinder coil pipe but with no guarantee that would fix it.

    Any advice/suggestions appreciated.

  2. andy48

    andy48 Screwfix Select

    1. If you can get hot water by using the immersion heater, then water is flowing from the cold water storage cistern in the loft into the base of the hot water cylinder, being heated and coming out of the top. So no problem with the water side.
    2. Which suggests a circulation problem with the primary circuit of hot water from boiler through coil in hot water cylinder.
    3. Could be:
    3a. Airlock in the cylinder coil.
    3b. A hidden diverter valve which has failed. Under the airing cupboard floor boards?
    3c. A faulty cylinder thermostat.
    3d. A blockage in the pipework.
    4. We need more information to help further:
    4a. What boiler is it. Make and model.
    4b. What controls are on it. Programmer?, cylinder thermostat?
    4c. Some photographs of airing cupboard showing pipes and controls. One with an overview, others with more detail.
  3. Steveb2006

    Steveb2006 New Member

    Thanks for the reply...

    The boiler is a Glow Worm 45-60
    The controller is a Drayton LP522 (new Jan 2020)

    There is no cylinder thermostat, nothing on the body of it, just the inlet and outlet pipes and switch for immersion heater.

    No sign of diverter valve - is there bound to be one in such a system?. There is the CH pump under the floorboards by the boiler.

    Ive attached this diagram Ive made of the actual system, accurate except that the cyclinder (in the airing cupboard) is directly above the boiler (in the kitchen). Plumbing3.jpg
  4. andy48

    andy48 Screwfix Select

    If your system has no motorised valves and the hot water is gravity only, has the new controller had its link set to the correct "G" position? (Back of controller)
  5. Steveb2006

    Steveb2006 New Member

    Yes the little jumper switch thing is set to "G". The hot water problem predates installing the new controller - but worth checking as I couldnt remember doing the setting.

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