I'm currently draining my heating system (radiator valve sprung a leak), however I have left it for a ages (1 hour) and it is still going, when I turn the bleed valve on an upstairs radiator air does not suck in but water sprays out.

I've got a cold water tank in the loft, a hot water cylinder upstairs and boiler downstairs, and am draining from a downstairs radiator, I live in a 3 bedroom detached house with 7 radiators.. I've turned off two valves next to the hot water cylinder, 1 feeds from the loft into the bottom of the cylinder, another feeds from the loft into the heating pump, I've also tied up the gall valve in the tank upstairs.

Is this purely a waiting game, or is there still water being fed into my system from somewhere else?

  • 1
    The boiler should have its own feed supply that needs to be turned off
    – d.george
    Apr 24, 2018 at 13:25
  • I've been in the same situation (although it was a combi boiler, not a cylinder and tank). I had problems with the drain valve that didn't open properly so had to take that apart. Fortunately it was in the garage so a bit of water on the floor didn't matter. Eventually I was able to open the bleed valves on the upper radiatiors and they stopped spraying. Might have taken an hour or so. Have you confirmed that you task isn't filling back up? Could you estimate how much water your draining and compare that you the volume of your system?
    – Carl
    Apr 24, 2018 at 17:11

1 Answer 1


My mistake, turns out that the heating had another smaller tank in the loft hidden behind the big tank and was filling up to compensate.

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