Rainwater Harvesting

Rhodes University has started a programme of installing 5000 litre tanks to harvest rainwater off rooves on campus, where reasonably practicable.

Drinking Rain Water

RU Clean Rain Water Tanks: Refill your water bottle with clean rain water - view map of RU Clean Rain Water Tanks.

Health considerations: Rainwater is considered to be safe source of drinking water; almost no accounts of illness are associated with drinking it.

• Mineral content: rainwater mineral content depends on local air quality. It tends to be 'soft' (low mineral content). 

  A layered filter system (e.g. Water Well or Hydro Health) with Ceramic Dome, Carbon Filter & Mineral Stones will add in essential minerals. 

• Asbestos: There is no asbestos-related disease linked with long-term consumption of rainwater harvested via asbestos roofs, gutters or tanks. 

  More info: long-term research findings,asbestos affects mainly lungs, EPA proposed concentration, asbestos natural occurrence,

• Bird droppings: There is negligible risk of contracting disease from bird droppings, as any avian enteric organisms will quickly be denatured through heat and dehydration on the roof. 

  More info: conference paper, Civil Research Group.

• Mosquitoes: Prevent mosquitoes and other invertebrates breeding in the rainwater tank by installing a Top-Filter system (see below).

• Rats: Eliminate the risk of rats entering the rainwater tank by installing a Top-Filter system (see below).

Harvesting Rain Water

RU student society, Galela Amanzi, raises funds to install rainwater tanks in Grahamstown East. Many Grahamstown residents install rainwater tanks at home. The following is required:

• Roof: 10 mm of rainfall on a surface area of 100 m² will yield 1000 litres.

• Gutter & downpipe: Essential for capturing and guiding rainwater to your tank.

• Filtration: Debris and dust on the roof should be filtered before it enters the tank - place between downpipe and tank inlet. This will keep the water clean (free of dirt, debris, droppings, rats, mosqitoes, etc) and odourless (anaerobic microorganisms do not grow in clean water). 

  Options: Water Rhapsody Rain Runner | Rain Harvest First Flush Diverter | Hydro Dynamics First Flush Diverter | make your own First_flush_bucket or Top-Filter system (see below).

• Rainwater tank: Use a good quality tank, preferably with black lining to prevent growth of algae.

• Tank stand: A correctly constructed base provides stable support; if possible, allow sufficient space for a bucket under the tap.

• Tap: plastic irrigation tap is less likely to be stolen; include fitting to attach hosepipe if required.

• Overflow: Attach a thick black pipe to overflow outlet, then an adaptor to connect it to a length of thin hose-pipe (guided into any part of garden as desired; long thin pipe prevents unwanted creatures entering tank)

Low-cost, low-maintenance Top-Filter system:

1. Cut a 25 cm diameter hole in the rainwater tank lid;

    Fine flat sieve beneath coarse convex sieve

2. Fix a flat fine mesh over this hole ("stainless steel 316 mesh" is durable, does not rust, available at engineering outlets) - to catch very fine dust & dried bird droppings, and exclude mosquitoes;
3. Fix convex coarse sieve on a hinge above fine sieve - items like leaves & twigs bounce off; and excludes rats;

   Downpipe suspended above sieve system

4. Suspend downpipe approximately 12 cm above the 'filter system' (as water emerges, there is space for debris to bounce away).
5. Maintenance: About once a year, remove lid and gently scrub the fine sieve with a brush and water to remove dirt. 

More INFO

• Rainwater Harvesting FAQ’s answered by Water Rhapsody

• Roofwater Harvesting: A Handbook for Practitioners by TH Thomas and DB Martinson (2007)

• Rainwater Harvesting research at the University of Warwick

• Rainwater Harvesting conference paper

Go to the Rhodes University ENVIRONMENT front page. Suggestions/Questions? Contact environment(at)ru.ac.za