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    Adding a Granny Flat or Cottage? The Plumbing and Electrical to Plan For

    Building a granny flat or garden cottage in Johannesburg? The water, drainage, geyser, DB board and metering decisions to get right early — and why they need COCs.

    2 April 2026 7 min read
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    A granny flat or garden cottage adds real value and income — but the parts that cause the most expensive headaches are the ones buried in the walls and ground. Plan the plumbing and electrical early and the build goes smoothly.

    Plumbing: drainage first

    The flat needs its own water supply with isolation, a hot-water solution (geyser or heat pump) sized for the unit, and kitchen/bathroom fixtures. The critical decision is drainage — tying the waste correctly into the existing sewer or municipal connection with the right falls. It's the hardest thing to change later, so get the route right before you build.

    Electrical: a sub-board makes sense

    A separate sub-distribution board for the flat gives you safety, isolation and the option of sub-metering. It's fed from the main supply and must be wired and certified to SANS 10142 with an Electrical COC.

    Sub-metering for rentals

    If you're renting the flat, a prepaid or check meter lets you recover or monitor the tenant's electricity (and sometimes water) usage separately. We can install it as part of the electrical work.

    COCs for both trades

    The electrical needs an Electrical COC, the plumbing (especially the geyser) a Plumbing COC — for compliance, insurance and future transfer. We do both trades and the certificates. See our work or plan your granny flat with us.

    Frequently Asked Questions

    A granny flat needs its own water supply connection with isolation, proper drainage tied correctly into the existing sewer or municipal connection with the right falls, a geyser or hot-water solution sized for the unit, and fixtures for the kitchen and bathroom. Planning the drainage route early is critical, as it's the hardest part to change later.

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