Please help; upstairs has 1 rad on landing (hot), next is the toilet (hot),small bedroom barely luke warm , 2nd bedroom barely luke warm ,finally main bedroom stone cold. when bleeding main bedroom rad a constant flow of water comes out with no hissing. However in the small and 2nd bedroom the water comes out with hissing also not a constant stream.I have been bleeding said rads but it doesn't make any difference to the rads heat.I seem to have emptied bucket loads of water from the system - is this right?-do i just keep on doing what i'm doing untill the air goes?
It sounds as if you might be getting some air in as you bleed. I assume that it is a vented system with a small feed/expansion tank in the attic - rather than a sealed system with a filling loop and expansion vessel?
Make sure that there is some water in the feed/expansion tank - at least a couple of inches to cover the outlet, but not too much - and that the ball valve isn't stuck. [If this tank becomes empty, you'll suck air rather water into the system when you open a bleed valve].
If there is a tap or gate valve on the feed pipe from the feed/expansion tank into the system make sure it is open.
You could have an air lock in one pipe to each rad, which doesn't clear when you bleed it because the replacement water comes via the other pipe. In order to eliminate this possibility, bleed each rad twice - once through each pipe. In other words, turn off one valve and bleed until you get a steady stream of water - then close that valve and open the other one and repeat the process. Finally open the other valve and, if the system has been balanced, make sure you leave the lockshield valve in the same partially open position as when you started. [When you close the lockshields, count how many complete and partial turns it takes to close them, so that you can subsequently open them again by the same amount].
If, when all the rads are fully bled, some still don't get hot, you may have to re-balance the system by turning down the lockshields on the hottest rads to increase the resistance of these - which will provide a bit more urge for the water to flow through the cooler rads. It will always take the easiest route round the system!
The need for radiators to be bled, is usually shown up by the fact that the lower section will become hot, whilst the upper section stays cold where air is trapped. They idea is to simply let the air out and and stop when water appears.
When the heating is actually running (boiler firing) you should be able to feel the hot water appear in the pipe as it makes its way to the radiator. Each radiator has two valves, one for turning it on and off, the other (which is identical, apart from lacking a handle) is for balancing the flow.
Your problem could be that either of the above valves are turned off, or you have an airlock (a bubble of air in the pipework). To solve the latter problem.... Make sure both valves are open on the problem radiators, turn off all the other radiators in other rooms, then run the heating. This should ensure airlocks are cleared. If this works, try bleeding the radiators again.
There are a number of possible problems (and attendent solutions) here. To determine which is likely, we need to know whether this behaviour has always existed, has existed since some work was done to the system, has suddenly occurred, or has built up over time.
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