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Help draining down Central Heating system

Discussion in 'Plumbing and Central Heating' started by MMarve, 13 Feb 2019.

  1. MMarve

    MMarve

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    Good morning all,

    I needed some helpful advice and apologise in advice if my current level of understanding makes it clear I have no idea what I am talking about.

    I recently moved into my house and am not 100% sure of how my heating and hot water is set up but am trying my best to get my head around what is doing what. I have a leaky trv body on the radiator in my hallway so need to replace that. I'm relatively comfortable with buying the replacement part and physically changing it but what is causing me some pause for thought is the need to drain down my central heating system.

    So this is what I have and how I understand it currently. I have a Valliant Eco tec boiler in my kitchen and a magiflow hot water cylinder in a cupboard in my bathroom. I don't have anything in my loft. So my understanding is that I have a sealed system. The hot water cylinder has immersion heater elements but these are turned off so I assume they are just as an override in the event that I have a problem with my boiler, I can flick those on and still have hot water as a back up. So currently the hot water tank is supplied with hot water from the boiler, then the hot water tank supplies hot water to the downstairs bath, shower and sink and the upstairs shower and sink. Then I think the boiler supplies hot water to the kitchen sink (I assume this as I hear the boiler kick in everytime I turn the hot water in the kitchen on) and also the hot water cylinder and the central heating. I am assuming that the hot water tank is not linked to the central heating at all.

    So, to drain down the central heating, I would need to locate my drain valve, connect a hose to a suitable drainage point, turn everything off and then open the drain valve and starting with the radiators upstairs, start opening the bleed valves, and continue until no more water drains out. The problem being that I expected to find a drain valve on a radiator downstairs but I have not. The only place I can see one is on the inlet and outlet of the hot water pipes going into the boiler. But as the boiler is hung on the wall in the kitchen, it would not seem to be the lowest point in the system so surely that wouldn't drain the whole system?

    So what am I missing? What am I not understanding properly? Is there a another drain valve somewhere and I have just not looked well enough?

    TIA
     
  2. ianmcd

    ianmcd

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    you dont need to drain the system just drop the pressure to 0 and put some towels below the valve as some water may come out but not too much, close the L/S valve at the opposite end of the rad then swap the valve over
     
  3. MMarve

    MMarve

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    Ohhhh, now I like the sound of that type of solution! So how do I drop the pressure to zero? Open a bleed valve, catch the water and wait for the boiler pressure to drop to zero?
     
  4. ianmcd

    ianmcd

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    yes that will do it just leave it open till no more water comes out, when you close the L/s valve on the rad count how many turns to close then open the same amount of turns in case it has been properly balanced
     
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