hi anyone,i want to fit a pump for a shower cubicle with shower and jets,the plumbing all seems to be in good order.the cold water tank is in the attic but not directly above the shower, it will need a horizontal run of approx 3m then a vertical run to the pump of about 1m,the hot water tank is in the airing cupboard next to where the shower will be fitted. the hot water tank is a good size but not sure of exact size?how do i work out the size of pump i will need??