by Dave From Leeds »
Tue May 12, 2009 5:34 pm
Hi plumbhome,
You probably have an airlock in the heating coil inside your hot water cylinder. Two possible things to try.
First, find two pipes going into one side of the cylinder one directly above the other. Then slacken, but do not remove the union on the top one. This may allow the air to be pushed out by the head of water in your central heating top-up tank in the same way as bleeding a radiator. Once water starts to dribble out as well, wait until any air bubbles subside then re-tighten the connection. This may well solve your problem.
If the above doesn't work, a more complicated method would be to locate your CH top-up tank (F&E tank) This will be the smaller of two cold water tanks probably in the loft, but certainly higher than the HW cylinder. Fix one end of a hosepipe over the open end of the vent pipe that goes over the top of the tank with the other end attached to a mains water fed cold tap. Then get an assistant to slowly open the tap whilst you observe the tank from above. Air bubbles should come in through the outlet at the base of the tank. Once these stop, turn off the tap and all should be OK. Do not open the cold water tap too far or the flow of water up into the F&E tank may be too fast for it's overflow to cope.
Someone else recently had this same problem and fixed it using the second method. Good luck.
