Rainwater Harvesting FAQs

1. How do I make a rainwater harvesting system pay for itself (amortize its cost) and why should I not just harvest rainwater for irrigation.

Simply by collecting and using water harvested during the rain season and using this water in your whole household, the tank surges full very rapidly, but you draw water from the system every time you open a tap, flush the loo, or 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! We also make sure that you don’t unnecessarily install too many rainwater tanks so that these never have enough roof area and rainfall to fill. I.e. you draw them as fast as they recharge.

2. Why do you recommend collecting rainwater?

There are as many environmental reasons associated with rainwater harvesting as would befit a super PhD thesis. However one very important reason is to reduce stress on our estuaries from less extraction from rivers during the rain season if everyone should harvest rainwater from their roofs rather than using municipal water. It is also very important to provide the means to become as independent as possible from the municipalities supply, at the same time guaranteeing a supply in lieu of possible and likely water outages in the near future.  

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 with a thatched roof. Tiled roofs are not as efficient as metal for collecting rainwater. Here are the average calculations

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

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

Whatever your roof, we are able to determine precisely how much storage of rainwater you should need. 

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

Our computer models determine the volume of rainwater storage you require depending on the following factors:

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

What is the size of roof area? The greater the area from which you can harvest the greater storage capacity you can viably install.

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

Is your house a holiday house or do you live in it all year round? Holiday homes will naturally have greater benefit from greater storage.

Do you have our other systems to conserve water? You can halve your usage! Our other systems of conserving water will enable you to reduce your use of water (draw down) from 240 litres per person per day to 120 litres per person per day without changing your lifestyle. These systems include Grey Water for irrigation purposes; and the Pool Tank to re-use swimming pool backwash water. One other product to make rainwater go further is our system to re-use grey water for toilet flushing. Your stored water will then go at least twice as far.

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, 1,500Litres, and include 2,500Litres, and 5,000Litres. Though 10,000L water tanks units are available this size is very unwieldy. We decide for you as to the best size.  

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

Downpipe filters are fixed to each and all of the downpipes, to initially harvest the rainwater. This water is fed into rainwater storage tanks, and we supply a very reliable system to pump this water from the rainwater tanks to the whole household.  

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. If you do recycle grey water from your house to your garden for irrigation purposes, 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 stand at a wall of your house under the roof eaves. Our system to harvest rainwater makes use of a filter installed in the downpipe. This filter is central to being able to harvest rainwater in a sustainable way. You are able to fill a rainwater tank or multiple rainwater tanks without the need for any pumping at all. You simply make use of gravity to make your rainwater harvesting sustainable. The filter is crucial to this end, and will deliver water to any place around you house or garden so long as the head of the filter is higher than the head of the tank, harvested rainwater will then be delivered in an underground pipe from the house to your tank in a ring main. All pipes from the filter around your house or commercial building are teed into the ring main.

Our filters therefore makes complete system of harvesting rainwater simple, sustainable and safe.

Our filter is a self cleaning device placed in your downpipe to send harvested rainwater in an underground pipe to water tanks without any chance of the delivery pipe blocking or clogging in any way. The filter receives the water, sieves out any debris and delivers this water via an underground pipe to your remote water tank.  

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

We provide all systems to harvest the rainwater, the underground piping from the gutters to the tanks, the rainwater storage tanks, and a pump to pressurize the water for the supply to the building. The pump starts soon after you turn on a tap, and switches off after all taps are closed. This is all automatic.

10. What is involved in the installation?

Installing our filters to harvest rainwater into each downpipe.

Supply and installation of suitable size and number of rainwater tanks.

Pump to deliver the water to the house. If you have need for high peak times of water usage we can install more pumps in parallel to increase the higher volumes required.

Electrical supply point.

A ball valve to augment supply in the water tanks from municipal mains. This gives you an emergency supply at all times.

An manifold to revert to municipal mains should your rainwater be exhausted.

11. How much does the system cost?

We have a set of costs to help you build a price for our rainwater harvesting system.  The price includes:

a. Downpipe Filters:

b. Water Tanks:

c. Pump including manifold

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, washing machines, dish washers, 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. Our system of harvesting rainwater ensures that you can hide these rainwater tanks anywhere in your garden.

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

Underground water tanks are available, but are expensive, and have the potential of popping out of the ground when empty.

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

Yes, under certain circumstances but under 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 so overloaded on the whole, that introducing extra water in the form of rainwater into the sewers is preposterous. Stored rainwater may be trickle fed into a Grey Water System, and this saves having to purchase an extra pump to lift the rainwater to a spraying head.

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

Yes, we now have several 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 unique system provides for an emergency municipal supply in the same rainwater tanks, should you run out of rainwater. This system of the emergency supply works automatically to give you this emergency supply at all times in spite of the authorities using water outages as a means of demand management.

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

We supply and install a ball valve to introduce water into the water tanks for an emergency supply at all times. This water may be used freely and copiously. If you anticipate that you will not have rain for a long period of time, or you experience a power failure, we provide you with a manifold to revert to municipal water. This consists of a single “cross-over prevention valve”. We cater for every possible eventuality.

19. What about water outages: How can I use the system of rainwater harvesting to save me from being affected by water outages when the municipality turn off water in search of ways to reduce demand?

We provide you with a ball valve inserted in a low position into one tank from the municipal source of water. This will provide you with one days use of water, enough to see you through a period of outage. When the rainwater runs out, the municipal water takes over automatically, providing emergency supply


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