Swimming pools and fountains (§702) — zones, SELV and supplementary bonding

The 701-bathroom guide covers the zone layout around a bath or shower. §702 sets similar but stricter requirements for swimming pools, fountains and comparable basins — a wet environment where people are often submerged with a large part of their body, giving a correspondingly lower body-resistance level than in a shower.

The three zones

Zone	Boundary	Permitted supply/equipment
Zone 0	Inside the basin itself (the water and its lining)	SELV only, maximum 12 V AC or 30 V ripple-free DC
Zone 1	Up to 2 m horizontally from the edge of the basin, and up to a certain height	Limited equipment suitable for wet environments; higher voltages than zone 0 are permitted under conditions, but with reinforced protection requirements
Zone 2	A further 1.5 m beyond the boundary of zone 1	Less restrictive than zone 1, but still with reinforced requirements compared to a normal indoor space

Diving boards, slides and similar fixed features can locally extend the actual zone boundaries beyond the bare 2 m/1.5 m dimensions, because the reach of a person using that feature is also taken into account.

RCD mandatory in all zones

Unlike bathrooms, swimming pools have no exemption route at all for protection by automatic disconnection: every circuit supplying equipment in zone 0, 1 or 2 (for example a filter pump, underwater lighting supply outside zone 0, or a sauna/hot-tub heating element) must be protected by an RCD with an operating current of at most 30 mA.

Supplementary equipotential bonding: no exemption possible

The 701 guide describes that supplementary bonding in a bathroom may be omitted under specific conditions (for example if all circuits are already protected by a 30 mA RCD and the main bonding is demonstrably intact). For a swimming pool that exemption does not exist: supplementary equipotential bonding between all conductive parts in the zones is mandatory at all times, regardless of which other protective measures are already in place.

Note: this article gives the zone framework as laid down in the core of IEC 60364-7-702 (on which the Dutch §702 is based). The exact dimensions for non-standard basin geometry (an irregularly shaped pool, a basin with a deck built over part of it, or a whirlpool built into a terrace) and the precise exceptions for certain bath types require consulting the full standard.

Practical relevance

When installing or renovating a swimming pool installation (filter pump, underwater lighting, a possible heat pump for the pool water), the first step is establishing which zone each part of the installation physically occupies — this determines both the permitted supply voltage and the IP protection rating, and whether supplementary bonding must be connected to that specific part.

Common mistakes

Connecting underwater lighting to mains voltage in zone 0 — only SELV (12 V AC/30 V ripple-free DC) is permitted in zone 0, regardless of the luminaire's IP rating.
Omitting supplementary bonding "because a 30 mA RCD is already present" — for a bathroom this may be possible under conditions, for a swimming pool never: §702 has no exemption route.
Measuring the zone dimensions only from the waterline without accounting for a diving board, slide or other fixed object that extends a user's reach — and therefore the actual zone boundary — beyond the bare 2 m/1.5 m dimension.