Ricochet News

There’s more to rainwater harvesting than buying a tank

Apr 10, 2018
There’s more to rainwater harvesting than buying a tank

Day Zero may have been pushed back indefinitely, but many people are still taking sensible precautions to adapt to the reality of living in a region and country where water supply is by no means guaranteed.

By now most responsible Capetonians have implemented all the short-term measures they can to achieve the City’s target of 50 litres per person per day – because they want to be good citizens, avoid crippling fines or the enforced installation of water-management devices.

These measures include only flushing toilets when necessary and then doing so with grey water, limiting shower times and collecting the water in a bucket, washing clothes less often and only when there’s a full load, and driving a dirty car – amongst others.

Nearly everyone who owns a swimming pool has long since covered it and many have come to terms with the reality of a green pool once the water level drops below the weir and there’s no way to filter.

Now with the immediate crisis averted, some homeowners are starting to think longer-term, considering the ‘what-if’ possibilities should there not be sufficient winter rainfall to fill the dams enough to see the Western Cape through next summer.

For a lot of people this means harvesting rainwater during the winter, so they have some sort of reserve should the winter rains not deliver and more draconian restrictions are imposed next year, or worse, Day Zero becomes a reality.

Judging by the number of trucks carrying large plastic water containers, the most common solution is now-generically named JoJo tank.

While it may seem a practical, easy option, installing a tank, or ‘rainwater harvesting system’ requires a little thought and preparation.

The first thing is to consider the costs, says Marlies Kappers, head of marketing for financial services provider, DirectAxis.

“Depending on the capacity and where you’re planning to put it, there may be more to this than just buying the tank,” she says. “It’s why getting some expert advice or doing some research at the outset could save you costs in the long run.”

The first step is to determine what size tank is best. For roofs between 50m2and 100m2a tank between 750 and 2 200 litres is sufficient. Roofs, between 200m2 and 400m2 will require tanks with capacities from 2 500 to 10 00 litres.

People forget that water is heavy. A cubic metre of water weighs a tonne. This means that if your tank is sitting on uneven ground, or soft soil that settles, it could easily tip over. Not only will this waste any water you’ve collected, but could damage the tank and the guttering running to it.

If you’re not setting the tank on an existing brick or concrete surface, you will need to first build a base or plinth that is at least 150mm thick.

It’s also worth considering how you’ll get the water from the tank to where you want to use it.

The best option is to try and situate the tank at the primary downpipe. If this is higher than where you need the water, such as the pool or vegetable garden, you can take advantage of gravity flow. Of course, because gutters run downhill, this isn’t always possible in which case you may need to consider a pump.

Again, this is where it is a good idea to get some expert advice, as a poor quality pump or one that’s doesn’t have enough capacity could cost you more in the long run.

Marlies says that with growing awareness about water scarcity, installing a rainwater tank is not only a sensible precaution, but could potentially add to the value of your home.

“Unlike a lifestyle improvement such as building a Jacuzzi, which might only appeal to you, the ability to harvest and store water is a practical benefit that may not only see you through an emergency, but could help to offset rising water costs and pay for itself over time.”

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