Filling A Vented System?

Hi,

My brother asked me to remove some radiators while he decorated. I simply closed the valves at each end of the rads, cracked the nuts and drained the water from the rads and removed them.

I went to re-fit the rads and fill the system, re-attached the rads, isolated the feed to the header tank in loft and put inhibitor in header tank. I then opened the rad valves expecting the header tank to empty into the system after which I would re-open the feed to the tank.

So far so good, I cracked the valves on one rad, loosened the vent and it filled. I went to the next rad and did the same, this time it only filled halfway and then the venting stopped so I thought the header tank must now be empty, so I went to the loft but the tank was still full.

Now I can only think that the water that entered the 1.5 rads was out of the pipework, but I cannot understand why the header tank won't 'gravity feed' into the system.

Any help would be appreciated!

Stbd 10

COmmon situation. Start the heating with the boiler itself turned off and the pump will probably shift the air lock. Else do search on Air lock.

Or you may have a very common prob, where sediment has settled in the supply pipe and gone hard, this always seems to happen where the 15mm pipe from the F&E cistern joins the big pipes, the join is usually near the pump (on the suction side) and can be in the airing cupboard or by the boiler. I'm told that a magnet will stick to the copper pipe where the blockage is.

In my case I had a tight manual bend in the 15mm pipe, which was where the blockage happened, but it can also be in the T.

If your joints are compression you can take apart and prod with a coathanger; if soldered it's easier to cut out (neatly) and rejoin with compression fittings. (resoldering wet pipes is not very succesful IMHO). Get a Pipeslice, some fittings and a small tub of jointing paste before you start. Either bale out the header tank or put a rubber bung in it, otherwise, when you cut or open the joint, a couple of galls of water will squirt over you and spoilk the carpet and celing beneath.

Thanks for the advice, I'll try what you have both said and let you know how I get on.

Cheers!

Stbd 10

The problem is sorted now, it was a blockage as described by JohnD.

Thank you both for your kind assistance!

Stbd 10

Find a draincock on the system, fit a hose pipe, insert a wine cork into the expansion pipe at the tank and turn on the main water, it should reverse the blockage for you, other than thet you will have to cut the joint where the cold feed enters the system. Are your rads in teh loft? have you got enough posotive head?

too late, Pete he's already fixed it!