To fit one of these units the cold water tank will need to have 25 gallons min capacity and minimum 8cm head above the shower unit, you will also need to use 10mm cable for the electrical feed, do you suffer low mains water pressure, if not it would be less hassle to fit a good 10.5 kw shower on the mains water feed you already have, just dont forget to check the cable and rcd/mcb size are up to the job/regulations first.
H.I.S.
December 2008