I want to add control thermostats to my radiators ,i live in bunglow and have a sealed system in place .the system works on oil,and the boiler is housed outside slightly elevated .I know how to release the pressure at the boiler,but there is no drain off cock on the heating system to let the water out of the heatihg system .Can anyone help ?
If the pipes come up from the floor then you will be able to drain all radiators together, turn off one radiator - with a dust sheet to catch any water and you may also need another pair of hands if you've never done it before - undo the nuts connecting the valves to the radiator, placing your thumb over each end - lift the radiator off and empty outside. Then you will be able to connect the hose to the radiator valve using 15mm pipe, nut and olive or similar depening on whether the radiator tails are 1/2" or 3/4" - open valve and the system will drain
If the pipes come down to each radiator from the loft you're going to have to drain each one individually.
As rosebery says buy the radiator valves which incorporate a drain point, it'll be much easier for future work.
the radiators are fed from under the floor,i shall work on one of the smaller rads. If i place a hose on the feed end to empty the system,do i need to do the same on the return end ? do i need the pump on ?