you can drain the whole system from a drain cock off one of the radiators. or just drain that rad. if you shut the lockshield valve on one end of the rad, then shut the thermostic valve right down. slacken one of the nuts between valve and radiator and drain into a paint tray or bowl depending on space, only drain slow so you can do nut back up to empty bowl. make sure you have some rag down if the carpet is still down cause the black muck in the bottom of rad is a pig to clean off. then when you replace rad tighten all back up open valves, then get pressure back up to 1.5 bar on your boiler using filling loop and bleed rad.
sometimes the thermostatics can open if the temp drops to low so before you start undo the knurled nut under the plastic top half of the valve and you can see a pin sticking up get a 5 pence and place that inside valve and screw back on and screw the dial down to 0. that stops the valve opening if it turns cold.
hi-spec plumbing, April 2007
