a good way if you have a air lock in your system is to get a short hose pipe and put one end to the water supply on the ball valve and the other end to the water connection to the heating system on the tank and force the mains pressure water down the pipe and it will come out of the vent pipe trying this a few times works for me.
young plumb
February 2010
howtomendit.com for free repair help, information and advice.
