You don't have to, but make sure your supplementary bonding is continuous, radiator, buthtub, copper pipes, Electric shaver socket, any exposed conductive parts have to be bonded
Hi MICK101,
Becasuse electrical shower should be on a circiut independant to it's self, earth does need to be terminate back the fuse/mcb at CU.
Regards
KB
MICK101,
you have to run a short lengh of 4mm cable from copper pipe (using earth clamps) suppling water to electric shower and terminate at the el. shower's earth terminal. Keep the bonding continuous, from there (copper pipe) to buthtub, radiator, any exposed conductive parts