Quite regularly we get an airlock in the hot water cylinder and thus no hot water but the central heating continues to supply the radiators with hot water. On occasions I have loosened a nut on a pipe leading upwards from the top of the cylinder and this temporarily cured the problem but what can be done to cure this problem permanently?

How is your system set up? Do you have a coil for the central heat in the water cylinder? I don't understand how air gets in the cylinder and why it doesn't flow to the tap and out.

How is your system set up? Do you have a coil for the central heat in the water cylinder? I don't understand how air gets in the cylinder and why it doesn't flow to the tap and and out.

To be honest I wouldn't know, but I can tell you that there is a diverter valve( I think that's what it's called) on a pipe next to the hot water cylinder, which allows hot water from the boiler to be either sent to the radiators or to the cylinder when the thermostat on the cylinder registers insufficient heat.

Have a contractor install a good quality auto vent with scrubber.