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System Drain down advice.

Discussion in 'Plumbing and Central Heating' started by 600rob, 5 Aug 2017.

  1. 600rob

    600rob

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    Hi all,
    Im planning on fitting a some new radiators and TRV’s in the place I recently moved to and I need a bit of advice regarding draining down and refilling the system since ive only ever drained/refilled combi systems in the past and this one is new(to me)


    Regarding the system itself….… ive done a bit of research and I think the system is an open vented gravity fed system with separate CH and HW controls.
    Heres a couple of pics that someone might be able to look at and confirm for me.



    In the loft ive got one large tank with the inlet ball valve marked in as Tank A in my pic

    This is connected to a further two tanks of the same size via a link pipe at the bottom( tanks B and C)..…
    I think these serve as the supply for the hot water cylinder…..


    Then ive got the small feed tank for the CH at the forefront of the pic


    From what I understand, if I want to drain down the CH system to carry out the intended work I need to do the following:

    -make sure CH is switched off
    -tie up the ball valve in the small feed tank or isolate the supply if possible
    -open the drain cock (with hose attached) then drain down the system venting each rad from upstairs to down as the system empties.

    -Do i need to do anything with the large tanks?
    -Is there anything else i might have missed?


    I’ll probably have to spread the task of fitting the new rads and valves over a couple of weekends but i wasn't sure if the HW/CW system will be affected by the drain down.

    Would this be okay and will i still be able to safely use the hot water system whilst the CH is temporarily drained for a couple of weeks?

    Any advice appreciated.
    Cheers
    Rob
     
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  3. ianmcd

    ianmcd

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    You dont have a gravity system you have a fully pumped system, isolate the cold supply to the small F&E tank and then manually open the two zone valves (slide the lever across and lock it in the open position) make sure the electrical supply to your heating is off and open the drain down cock and start from the top opening the bleed valves on the radiators till the system is empty , refilling is the opposite
     
  4. 600rob

    600rob

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    Thanks for the reply and advice Ian

    Does that mean i wont be able to heat and use the HW while the CH is drained?
     
  5. seniorservice

    seniorservice

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    Looks like you've got an electric immersion element on the top of the hw cylinder. Turn this on to heat the water in cylinder whilst rest of system is out of action.

    Also, before draining down, make sure the small (F&E) tank doesn't have debris in it. If it does, bail it out and clean before draining down, or all this crud will lodge in your pipework.
     
    Last edited: 5 Aug 2017
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  6. 600rob

    600rob

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    I guess what i should have said is will i have to make sure the HW as well as the CH is switched off?
    And to use the immersion heater as a back up to heat the water?

    Sorry guys im not a plumber by trade.
    Thanks
     
  7. seniorservice

    seniorservice

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    Yes, make sure hw and ch are turned off on the programmer before draining down. There should be a separate fused spur to switch on for immersion element. Follow the wire from the black cap of element on top of cylinder to the wall. Immersion will heat water instead of boiler whilst system drained down.
     
  8. 600rob

    600rob

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    Great. Many thanks!
     
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