A couple of bucketfuls should empty the F&E and draw water out of the upper part of the system. If the F&E is very full, drain enough to empty it, then take out a bucket or two more. If the water you are draining out contains chemicals, you can always tip it back into the F&E later to re-use it.
The water level in the F&E only needs to be a couple of inches above the feed pipe when it is cold (it will rise when hot due to expansion). You can adjust the float arm to change the level.
Before turning on the pump check that the water has refilled your system, drawing in the chemical. You don't want the pump to be spinning dry, or the boiler firing with air in it. If you bleed the rads and water squirts out well from the highest rad, then the water has gone back in. Depending on your layout, the drained water will probably come from the cylinder coil.
p.s. the rubber washers in your drain valves might have perished and need changing, so buy a couple before you start and have a hose on the drain cock in case you can't close it again
I was unable ro find then in a DIY shed so I suppose you will have to find a plumbers merchant. They are a bit smaller than tap washers
The water level in the F&E only needs to be a couple of inches above the feed pipe when it is cold (it will rise when hot due to expansion). You can adjust the float arm to change the level.
Before turning on the pump check that the water has refilled your system, drawing in the chemical. You don't want the pump to be spinning dry, or the boiler firing with air in it. If you bleed the rads and water squirts out well from the highest rad, then the water has gone back in. Depending on your layout, the drained water will probably come from the cylinder coil.
p.s. the rubber washers in your drain valves might have perished and need changing, so buy a couple before you start and have a hose on the drain cock in case you can't close it again
I was unable ro find then in a DIY shed so I suppose you will have to find a plumbers merchant. They are a bit smaller than tap washers
