I've installed a new gravity fed hot water system in my bungalow, putting 22mm pipework to the bath taps to give a good flow rate. Although I raised the cold feed tank as high as possible, I seem to be getting air pockets from the bath hot tap when its fully open. Can I put a non-return valve in the expansion overflow to stop this, or is it better to simply restrict the hot water flow with a gate valve before the hot tap?