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We have changed a gas central heating radiator. It is the last radiator in the circuit. It will not communicate with the boiler and only brings hot water into the pipe leading to the thermostat when on constant bleed. I have taken ten buckets of water from this radiator with the thermostat on 5. As soon as I close the purger the hot water stops coming down the pipe.

Pipes run across the attic. All the other radiators heat to really hot and I have bled all the other radiators several times.

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I tink that means the drainpipe of that last one one is clogged... –  ratchet freak Nov 12 '12 at 10:43
@ratchetfreak that's probably worth an answer. I'd recommend checking the temp of the drainpipe compared to the inflow, and we should find out if there's any air still coming out while bleeding. –  BMitch Nov 12 '12 at 12:21

1 Answer 1

I believe that means that the drain pipe of that last radiator is blocked in some way (or simply not or incorrectly connected)

for the connection you'll need to ensure the inlet and outlets are connected to the proper pipes

if it is properly connected then this can be an airlock to fix this close all other radiators and turn on the pump this will increase the pressure before the air bubble and might clear it.

if this doesn't fix it you'll need to check the drain pipes and replace as necessary.

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