17th Edition of the IEE Wiring Regulations redefined the zones for
electrical equipment in bathrooms and must be used for installations
designed after 30th June 2008. They are now identified from 0 to 2, with
0 being the wettest - the previous zone 3 is no longer defined.
Zone 0 - the interior of the bath or shower that can hold water. Requires electrical products to be low voltage (max 12V) and rated IPX7.
Zone 1 - the area directly above zone 0, limited to a height of 2.25m above the bath or shower. Requires electrical products to have an IPX4 or better. Products should use safety extra low voltage (SELV) with the transformer located in zone 3 or beyond.
Zone 2 - the area beyond zones 0 and 1, stretching 0.6m horizontally and up to 2.25m vertically. Also includes the recessed area of a window with a sill next to the bath. Requires electrical products to have an IPX4 or better. SELV with the transformer located in zone 3 or beyond.
Zone 3 - the area beyond zone 2, stretching 2.4m horizontally and up to 2.25m vertically. There is not a specified IP number for this zone, although some products are marked as not for bathroom use. SELV or shaver units are permitted, all other portable electrical equipment is not.
701.410.3.5 The protective measures of obstacles and placing out of reach (section 417) are NOT permitted.
The regulation above can be understood to include, but not exclusively refer the placement of sockets within ZONE 1 (under or behind the tub base). The zone shall therefore NOT have items below IPX4, this includes sockets.
British Standard. Requirements of Electrical Installations
electrical supply for your steam shower or whirlpool bath must be via
an isolated fused spur that is switched outside of the bathroom. The
shower/whirlpool is delivered with a plug and RCD. The plug is for
testing only and MUST be removed in order to complete the installation
and to enable connection to the fused spur. The RCD can also be removed
if the electricity to the bathroom is protected by an RCD at the mains
board/ Consumer unit.
All electrical work MUST be carried out by a qualified Part P registered electrician and in accordance with current regulations. Failure to adhere to these regulations may cause serious injury, even death and will invalidate your product Warranty, it may also be illegal.