Blocked pipe or Air Lock

Just moved 2 rads (replaced one with a new rad as the pipe-work went under the floor of an extension and gave the odd problem cold unable to bleed out ) I an now having problems getting the air out not sure if have a intermittent blockage in supply or return pipe not sure what type the system is called boiler is wall mounted B/F 10 year old Ideal Classic pipe work 22m/m supply and return with a manifold with 4 rings of 8m/m pipes on each to the rads I had a problem last Christmas time 3 rads not working suspect a blockage in the 8m/m pipe-work from the manifold to the rads on that ring but one night the air locked moved and all was OK from then on .
Some of the rings are working both up and down the ring I have broken into does not warm up but bleeds and full of water.
Please could someone tell me to correct method to drain a system down
as closing the cold supply valve & opening the drain valve that drains down the boiler plus draining down the ring I worked on did not completely drain the system . I have just emptied by removed all the sediment from the expansion tank in the attic very dirty and replaced with normal water until `I can get the system to work properly .
Any suggestions would be very welcome

It sounds as though you may need a powerflush, those microbore pipes are the worst for this problem obviously as they are so small to begin with.

You might want to invest in some sludge remover ( Sentinel x400 is commonly used. ) Try putting that into the system to see whether or not you can clean it yourself without the expense of a powerflush.

It usually takes at least 2 weeks, with the c/h turned on, after this process if drained, refilled and successful you will need to the add inhibitor ( Again Sentinel X 100 is commonly used. ) to the system.

Thanks for your quick reply beans on toast will take on board what you said .
Will each Rad have to be drained in turn ? or should i open fully both valves and remove bleed screw ? to assist drain ?

Mike you have to run the system hot with all valves open for a couple of weeks.
Then drain via the lowest point opening up bleed valves up stairs to assist.
Renew with clean water then drain again and then add inhibitor.
Pete

Thanks for your reply Pete will start trying this when it cools down a bit regards ~Mike

I think Fluffy means you need to run the system for 2 weeks with the X400 in the system.

If you must use X400 then I would say 3-4 weeks. Much better is Ferroquest which does the job in 2-3 days.

Tony

Thanks for your Suggestions Tony will bear this mind when it cools down a regards ~Mike