Rainwater Harvesting

During December 2019 the SABS published SANS 1088 Water efficiency in buildings which will ultimately in one form or another become SANS 10400 –XB when the Minister for Trade & Industry updates the National Building Regulations. We anticipate this will commence during 2020. The standard applies to the following occupancy and building classifications as defined in SANS 10400-A;

  • A3 Place of instruction
  • E1 Place of detention
  • G1 Offices including banks, consulting rooms, etc. 
  • H1 Hotel
  • H2 Dormitory
  • H3 Domestic residence
  • H4 Dwelling house
  • H5 Hospitality

The amount to be harvested is dependent on location with the country having been divided into six districts categorized by mean annual rainfall. In addition to a map Table-3 lists all cities and towns, by province, by mean annual rainfall.

Tables 4a & 4b list the minimum storage capacity required per roof area for each category whereas Table 4c lists the additional requirement for swimming and spa pools. A further requirement is that pools have to be ‘potable water neutral’ i.e. not requiring the use of potable water other than for initial filling, top-up is to be from harvested rainwater plus pools requiring to be backwashed are to be fitted with a holding tank for treating and returning a minimum of 70% of the backwashed water to the pool. External pools to be fitted with a cover.

An important point to note is that in terms of the Water Services raw harvested rainwater is not considered potable and storage reservoirs are to be fitted with a warning sign to that effect.

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