Recently I am having problems were after a few mins my shower looses presure not completley but enough so cant really have shower properly, Also when I turn of the HOT water tap downstairs or in the bathroom it triggers the shower pump, I have lookded into this and it seems to be air getting into the hot water pipes, how and why is this happening?, and what can i do to stop this, I have normal heating system with 2 tanks in loft, hotwater cyclinder in airing cupboard and shower pump next to this, When shower is working it works fine although shower pump is very noisy but this is standard according to a plumber I know, I would love to take of shower pump and check if there is any blockedge, but the pushfit connectors do not have any isolaters on them so would have to drain whole system is this correct?.