The tradesman made me buy a single pump for increasing my shower pressure upon agreement that he will complete the job after the purchase. However, he seem to had lost interest after I had made the purchase and I had to return the single pump to the retailer costing me return delivery cost. However, on a positive note, I found another plumber who not only suggested that AA Plumbing had made me buy a incorrect pump (my system can only take a twin pump) but he could fix my shower pressure without the need for a pump; this saving me a good £200.