Problems Draining Sealed Central Heating System

4 Jan 2008
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United Kingdom

I have a house on 3 floors with radiators on each.

The wall mounted boiler is on the ground floor. The unvented DHW tank is on the first floor.

The pipe work from the boiler rises up to the ground floor ceiling.

Yesterday I needed to drain the system.

I switched off the mains power attached a drain hose to the drain outlet at the boiler.

I also moved all the 2 ports valves to their open position.

I opened the drain outlet and then opened the air vents on the radiators on the top floor starting with the towel rail first as it was the tallest.

The water drained out slowly.

Eventually I was able to open all the radiator air vents on the top floor and I could hear air being sucked into each radiator.

However I struggled to get the radiators on the first floor to drain ?

I was able to drain those where the 15mm tails came through the floor, but not those where the 15mm tails came through the wall ??

I was wondering if these might all be drop fed radiators ? It is a timber framed house.

I believe that the radiators on the ground floor are all drop fed at the boiler is above all of them ?

I was able to drain water from the air vents from the radiators on the ground floor. I think that this was the water in the drop feed pipe work and when it stopped the water in the pipework must be level with the water in the top of the radiator.

I had hoped that this would drain the first floor radiators but it did not ?

All the ground floor radiators are fitted with drain connections, but I could not get them to open and did not want to force them. This is a problem for another day.

For the first floor radiators I think that I now have no option but to close the TRV, close the lock shield ( keeping a count on the number of turns for re-opening later) then partially back off the nut to the lock shield valve and then first drain the feed pipe work whereupon I can then open the lock shield ( plus the air vent ) at the top of the radiator and drain the water from the radiator.

Does this make sense or am I missing something ?

As I can not see the main 22mm pipe work run I appreciate that I am guessing about some of this ?

Any help would be much appreciated.
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