hi anyone, i want to fit a pump to a new shower cubicle with side jets.how do i work out the correct size of the pump i will need? the cold water tank is in the attic and will need a horizontal run of about 3meters and the hot water tank is in the airing cupboard pretty much back to back with the shower.the hot water tank is a good size but not sure of exact size the hot water flow frow the taps is rubbish,more of a trickle than a woosh!