Draining & filling the system problem

[daveatdanby]

System Drain / Fill problems

I tried to drain down my central heating system as I had done in the past by opening the drain adjacent to the boiler. It normally takes about an hour to empty but this time the water in the loft feed & expansion tank failed to drain away, and after two hours there was still a trickle from the boiler drain.

I emptied the system by loosening a radiator valve.
I then did the pipe work alteration as I wanted to do.

The water in the header tank never dropped to the outlet.

A couple of hours later when I tried to fill up again the water would not drain down into the system.

I eventually filled the system up by connecting a hose from the mains to the boiler drain until water went over into the tank via the expansion pipe. The heating system is now working fine, but I am concerned that it will not feed from the tank if it needs to.
I am suspecting that the feed from the tank to the Mistral Oil boiler is blocked by sediment somewhere, if this is so how is the best way to clear it
.
Any other suggestions would be really helpful.

Thanks Dave.

 

[kevplumb]

blockage is usually at the point the feed pipe from the tank joins the system pipework

 

[gavinda]

cold feed and vent are usually just before the pump on most wet systems. look at your pump and work back from it... ther'll be a teed of bit of 15mm and then a teed 22mm. the 15 is where the blockage ll be.... stick a magnet on it and thatll give a rough location