not the thing to be doing with the weather we have at the moment. This applys to vented CH system. But if you must then isolate the header tank from the cold water supply. Switch off the boiler eelctrical supply and ensure that it cannot fire up.
Locate the drain cock, usually at the lowest point in the system. connect a length of garden hose to the draincock and direct the hose to drain. open the draincock and wait for the system to empty.
garryk, January 2010
