Rainwater tanks, greywater and borehole rules in Cape Town

Cape Town will not quickly forget the drought of 2017 and 2018, when the city came close to “Day Zero”. One of its lasting effects is that many homes now have rainwater tanks, greywater systems, boreholes or wellpoints. If you are building or renovating, it is a good time to include them. But there are rules, and they exist for good reasons.

Why there are rules

The main concern is protecting the drinking water supply. If a rainwater, greywater or borehole system is connected to your home’s plumbing incorrectly, non-potable water can flow back into the municipal supply and contaminate it. The City’s Water By-law and its guidelines for alternative water installations set out how to prevent this.

Rainwater tanks

Rainwater harvesting is the simplest system. Water from the roof is collected in a tank and used for irrigation, toilet flushing or, with treatment, other uses.

A stand-alone tank with a tap, used for watering the garden, is simple.
If the tank is connected to your house plumbing, for example for toilet flushing, it is an alternative water installation and must comply with the City’s requirements, including preventing any cross-connection with municipal water.
Large tanks are heavy and need a proper base. Tanks on stands or roofs need structural consideration.

Greywater

Greywater is used water from basins, showers, baths and washing machines (not toilets or kitchen sinks).

It can be used for garden irrigation, ideally through subsurface drip irrigation.
Greywater should not be stored for long, because it quickly becomes smelly and unhygienic.
Systems connected to your plumbing must comply with the City’s rules, and pipes and outlets should be clearly marked as non-potable.

Boreholes and wellpoints

Boreholes and wellpoints must be registered with the City, and the official sign with your registration number must be displayed where it can be seen from the street.
Sinking a new borehole or wellpoint may also need authorisation from the national Department of Water and Sanitation.
Water use should be metered, and records kept.
Borehole water must never be connected to your municipal supply. If it is used inside the house, it needs proper treatment and a fully separate system.

Signage

All alternative water outlets, such as taps supplied from a tank or borehole, must carry a sign showing the water is not for drinking.

Planning it into a build

During a new build or major renovation, alternative water systems are much easier and cheaper to install:

Separate plumbing for toilets can be run in walls before they are closed up.
Space for tanks and pumps can be designed in, rather than placed wherever they fit.
Gutters and downpipes can be planned to feed the tanks.

A plumber registered with the City should design and install connected systems, and issue a certificate of compliance.

Our approach

We include rainwater and greywater provisions in our projects when our clients want them, working with registered plumbers so the systems comply. If you are interested, ask us during the design stage.