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We moved in to a house around 6 months ago.

I noticed that our radiators were not getting too hot so went ahead and bled them.

I managed to eventually get water out of most of them however a couple of large ladder radiators I can completely unscrew and no air or water comes out.

What's wrong here?

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You add pressure to the system from the mains valve into the sealed system* - at this point even if the system is cold you can go right up to the top of the green, it won't stay there long, you're going to drop the pressure again any minute.

You can't bleed an entire closed system in one quick run round the rads, especially if it's been neglected for a long time.

Once pressure is back up, bleed all the rads again until pressure drops back to zero, then you rinse & repeat until you get no more air and the pressure is up.
Once this is settled, set the pressure to the middle of the green - you're still not quite done.

Then you risk running it hot [I know, that's the point you started from, but this time we have pressure & less air.] If the pump will run without the heat on, then do that instead - let it run a good hour or three. This ought to cycle air out of any traps & give you one more shot to bleed the whole lot again & set the pressure back to mid-green.

As you clear the traps, you should get to a point where the only air in the system is at the highest points, top floor.

Then you keep an eye on that meter & never let it drop out of the gren band - it will go up & down when the heating is on or off, but it needs to stay within it.

*Strictly speaking this should be disconnected when not in use, but practically people tend to just leave it connected & close the valves at both ends.

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  • Should be under the boiler. A link from the mains cold supply into the sealed part of the system. It should be on a flexi-hose not on copper, with a tap at each end. When not in use, should be disconnected but no-one ever does, just be sure to close both taps. [You don't ever want the heating water going back into the mains supply. Generally the mains pressure would be too much, but if they ever dig up the road, that could change things temporarily, but you don't want it intermixing]
    – Tetsujin
    Jan 6, 2022 at 19:44
  • Boiler should have a gauge too.
    – Tetsujin
    Jan 6, 2022 at 19:46
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    @user146829 Have you found a filling loop anywhere yet? If someone has been daft enough to put the filling loop a long way from the gauge, then the only option may be two people, one filling and one watching the gauge.
    – Simon B
    Jan 6, 2022 at 21:39
  • @SimonB - OP seems to have left the building. Guess we'll never know ;)
    – Tetsujin
    Jan 9, 2022 at 18:16

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