Gauteng and NW Province

Rainwater Harvesting FAQ

  1. How do I make a rainwater harvesting system pay for itself?

Simply by collecting and using your harvested rainwater during the rainy season in your whole house. The tank surges full very rapidly, but you draw water from the system every time you open a tap, flush the loo, use the washing machine or any other use of water. It removes the romantic notion of filling a water tank and not knowing what to do with the water, or trying to fill a water tank with harvested rainwater that is full already!

2. Why do you recommend collecting rainwater?

The list of environmental reasons are endless. One very important reason though is to reduce stress on our estuaries by extracting less from rivers during the rain season. If everyone could harvest half their rainwater from half their roofs we could turn the ‘demand exceeds supply’ issue around. It is also very important to become as independent as possible from the municipality.

3. What sort of roof should I use to maximize my rainwater harvesting?

The most efficient roof surface is a metal roof. This means a corrugated iron, flat iron sheet, or IBR profile. You cannot harvest rainwater from a thatched roof. Tiled roofs are not as efficient as metal, but anything is better than nothing. Here are the average calculations:

11 mm of rainfall for metal roofs produce 1000L of harvested rainwater for every 100 sq. metres of roof area and

16 mm of rainfall for tiled roofs produce 1000L of harvested rainwater for every 100 sq. metres of roof area

4. What size tanks do I need to store and use rainwater for my circumstances?

We will determine the approximate storage capacity you require depending on the following:

How many people are there in the house? The more people using water the less storage you need and vice versa.

What is the size of roof area? The greater the harvesting area the greater the storage capacity.

What type of roof do you have? The more efficient the surface the more you can harvest.

Do you have some of our other conserving water systems? You can halve your usage! Combined systems enable you to reduce your consumption from 240 litres per person per day to 120 litres per person per day or less without changing your lifestyle. These systems include the recycling of grey water for irrigation or toilet flushing, water saving toilet devices, and the recycling of backwashed pool water.

What is your rainfall pattern? How much and how often does it rain?

5. What water tanks sizes are available for the storage of rainwater?

The tank sizes for rainwater storage range from 750Litres to 20,000Litres. Space and aesthetics are important deciding factors.

6. What do I get in order for me to harvest, store, and pump rainwater to my house?

The complete system; from harvesting your rain water (via visible gutters and downpipes or fullbore outlets) and filtering of the rainwater to delivering the clean water to the whole household. A neat, complete A-Z, installation.

7. Will the municipality charge me for sewerage effluent if I use rainwater?

The municipalities charge for water and sewerage in a block tariff system. The more you use, the higher the tariff. Municipalities charge for sewerage based only on the volume (number of kilolitres) of water that you consume. They calculated some time ago (though very erroneously) that seventy percent of the water that you consume through your water meter is wasted into the sewer as treatable effluent. Whether you have a rain harvesting system or not, (for water consumed), they will only be able to charge you for the amount of water that has run through the water meter, and the same goes for the sewerage charge, at whatever tariff is applicable, based on 70% of that metered water. You will not be charged for the rainwater used at your house. Do not think that you are being unfair: The municipality will still charge you for the effluent portion of your metered water at the rate of 70%, even though you may be re-using grey water for irrigation purposes. As a matter of interest, grey water (water from baths, showers, hand basins and your laundry) and black water (kitchen, toilets and bidets) go in the same pipeline to the sewerage treatment works. When you recycle grey water from your house to your garden, you send as little as 5% instead of 70% of your consumed and metered water from municipal source into the sewer for treatment at the sewerage treatment works.

8. Water tanks are ugly! How can I conceal a tank away from my house, but still use harvested rainwater.

Water tanks no longer need to be installed right next to the house. We can install it anywhere you want. Also remember there are a variety of different tanks available. Our main suppliers are Heunis (galvanized steel water tanks), Urban Rain (beautiful tanks designed for urban living), Jojo tanks (good old Jojo – the best value for money) and Roto tanks (similar to Jojo, slightly different (more modern).

9. How do I pressurize the rainwater for household use?

A pump is included in the installation.

10. What is involved in the installation?

The complete system; harvesting and filtering the water from visible downpipes or fullbore outlets, complete underground reticulation system, lifting and replacing of all paving/ concrete, supply and installation of the water tanks, concrete base for tanks (ALL our tanks are installed on a solid concrete base), the pump (s) to deliver the water to the house/garden, electrical connection, emergency back-up supply, an override/manifold to alternate between supplies (rain and municipal) and additional filtration (3-stage or 5-stage to potable water – depends on the application)

11. How much does the system cost?

Each system is individually designed and quoted accordingly. Prices vary between R 6 000 – R 600 000.

12. For what purposes can I use the harvested rainwater?

Rainwater can be used for all household purposes, i.e. irrigation, refilling your pool, flushing your toilets, car washing, replacing municipal water etc.

13. Can I use my irrigation that I already have?

Yes, rainwater can go into your irrigation system as well as other household uses.

14. Do the tanks have to be stored underneath my gutters?

No. tanks can be installed anywhere in the garden.

15. Do the tanks have to be stored above ground?

No, underground water tanks are also available and pools can be converted into reservoirs.

16. Can I add the rainwater to a grey water system?

Yes, under certain circumstances but under very strict controls. The problem is the overflow. Excess rainwater should flow to a river, and excess grey water should overflow to the sewerage treatment works. You may not send grey water to a river, and our sewerage treatment works are already overloaded that introducing extra water in the form of rainwater into the sewers is preposterous.

17. How long does the system take to install?

It depends on the installation. An ‘average’ house can take 5 days, a school can take 5 weeks.

18. Can rainwater be used instead of and/or in conjunction with Council water?

Yes, we have numerous houses that live off the grid, providing total autonomy and independence. However we assure you of two things in this regard. First is to maximize the rainwater storage, and secondly our system provides for an emergency municipal supply in the same rainwater tanks, should you run out of rainwater.

19. How do I switch between my rainwater tank and municipal mains water?

We supply and install a manifold that enables you to choose between supplies.

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