You must first make sure the system has has antifreeze mixed in the radiators has you only drain the water in the combi the water left in the radiators must be protected from freezing with the correct amount of mixture.
Turn off the mains water and disconnect the pipe outside open up all taps flush toilets inc shower also disconnect shower hose washing machine garden hose ect.
At the boiler turn off electric at mains look for the pressure relieve valve a rednob turn it a quarter turn and hold the pressure indicator on the combi should fall to zero. leave all taps in open position.Good luck(Or get the site lads to do it)
Leon, September 2014
