plumbing advice please

[NEILAIDKEY]

Hi i was wondering if anyone could help me, i have an old back boiler that still works fine it is a open vented system with the tank in the loft, the water is set at correct leval when cold, i have a problem getting the rads to work tried a new pump had the rads off about 5 times hit them and washed them but to no avail. i took the floors up in the bed rooms and it seems the 22mm pipe is the main flo and return with the 4 rads branching of in 15mm, all except a new rad that was fitted about 10 yrs ago down stairs but not on the same run as all the others seems to have its own 22mm under bedroom floor comes down in 15mm to the rad and back up, it will heat up on its own but soon as you put the others on it goes cold.
i can get heat with all downstairs off and vise versa but not all together.
also i have been told that changing the pump to the flo and not the return might be better, any help on the subject would be most greatly recieved

 

[Bahco]

Try bleeding the pump or balancing your system.

Details on rad problems in the fifth post down. (FAQ)

 

[NEILAIDKEY]

Many thanks for your speedy reply, i have tried all or most of the solutions first of all when i switch the heating on from cold it only heats a few rads upstairs and then goes cold if i go round each rad that is getting hot and switch them of the heat moves on to the next and so on till one by one i can get them hot but as soon as i ballance them and try to get them all on together most of them go cold, with the floor up the feed pipe seems to be hot but the return is sometimes warm and sometimes cold. also when i drain down all the rads drain ok from a hose pipe in the lounge but 2 downstairs i have to drain them through the rad its self by undoing it with a bucket under yet are all connected to the main flow and return under the bedroom floor.last night i tried with all rads of and the loft was full of hot steam in the header tank should that happen.

many thanks for your help i know it must be hard for you to picture what is happening just by words on a comp but your advice is truly welcom

 

[namsag]

You say old system so is it still gravity hot water and pump only for heating .. If so on the flow pipe from the boiler usually within 2 feet there will be an anti-gravity valve about 3 inches in length and made of brass . These clog up and stick stopping rad circuit working . Take it out and change it

 

[NEILAIDKEY]

thanks for reply and sorry should have said the boiler has a timer switch so we can have heating and water or water on its own the hot water when heating and water on together is extremly hot and so is one rad when others off and so to with one rad at a time