In many cities where more that 40% of the Erf is covered with building or hard surface the cities require some form of rainwater/storm water attenuation system. Traditionally it was require to install a soak pit with a volumetric size of 1 cubic meter for every 40 sqm of hard surface area.
An alternative has now been established where homeowners can install rainwater tanks. They can claim 60% of the volume. An example A property 1000sqm is covered by 500sqm of hard surface. It will require at least (500/40) = 12.5 cubic meters for a soak pit. By installing a (12.5/60%) = 20000l rainwater tank they would not have to install a soak pit and can install a rainwater harvesting tank and use the water for general purposes.
It is not only cheaper to install rainwater tanks but the owner will save significantly on his water bill
