We have a conventional power shower setup with the twin impellor pump
in the airing cupboard next to the hot water tank. On top of the tank
is a flange with the right angle outlet going to the shower pump.

Sometimes the pump makes a strange noise and the shower goes slightly
cold and then hot before returning to the correct temperature
(Aqua-lisa themostatically controlled mixer). It sounds like air may
be getting in somehow.

However, the hot water tap in the shower room also sometime "splurts"
and bangs as if it too has air in it. The feed for this tap is taken
off the main tank outlet going vertically up from the flange. All
other hot water taps in the house are OK.

Anyone have any ideas about this ????????????