Gauteng and NW Province

Filtering, Placement and Types of Water Tanks

Positioning of Rainwater Tanks.

One of the biggest problems with rainwater tanks is their obtrusiveness. Most estates do not allow your typical Jojo / Roto tank to be visible and unfortunately the size of the bigger round tanks has made it impractical to have them standing on a property literally outside a door or window. The perception, despite their usefulness is that they are ugly. Fortunately there are various types and colours of tanks available that are designed for small gardens / walkways / limited areas etc. The beauty of our systems is that water tanks can be placed anywhere on the property; from the highest to the lowest point, it doesn’t matter. We design a system around your needs / HOA rules and regulations.

Water Tank Sizes

The size of the tank depends on the catchment area and system demand. Typical sizes are ranged in capacity from around 750L to 10,000L, or multiples of these. The most popular sizes are 2500L and 5000 litres, which are easily handled and are not unsightly.

Smaller tanks, such as the Slimlines (between 750L – 900L) or Urban Rain’s slimmer tanks are used when space is an issue/concern. These tanks can be used for the exact same purpose than the bigger tanks; an off-the grid system or a single tank to top-up the pool / flush a toilet.

Larger tanks are commonly used where there is a desire to go as off grid as far as possible. The storage capacity is based on a whole lot of factors e.g. roof type surface (tile or metal), roof area in square metres, number of people drawing water from the rainwater tank, whether or not you have more than one of our water saving systems in place to reduce the overall consumption, and whether the house is a home, holiday home or a commercial or industrial building.

To give an example of this calculation, (completed by actuaries): a typical metal roof will deliver 1000 litres of water from 100 square metres of roof for every 11 mm of rain. To get the same volume of water from a tiled roof one would need 16 mm of rain. Each middle class person uses approx. 240 litres of water daily, so the draw from the rain tanks is very substantial. If you install two of our systems e.g. rainwater off grid and recycling grey water for irrigation you can reduce the demand for water to at worst half of the 240 litres to 120 litres per person per day, but mostly down to as little as to 80 to 100 litres per person per day. Stored rainwater can go so much further without a change in lifestyle. The value of this calculation ensures that there is enough storage so that rainwater tanks need never overflow, and that one does not overspend on too many rainwater tanks that never fill. Climate change is very real and there is no standard weather pattern anymore. We seem to shift between drought and floods at the moment. This isn’t a problem, because our systems are all modular to fit your budget and to accommodate any possible overflows etc.

Types of Water Tanks

Many people use harvested rainwater for gardening applications e.g. irrigation rather than as a potable (drinkable) water surrogate. Please remember with the correct filtration process an off-the-grid system will give you a better ROI than that of a water tank for garden use only. Water tanks may be constructed from materials such as plastic (polyethylene), concrete, plastered brickwork, galvanized steel and stainless steel which are rust and chemical-resistant. By far the most popular and cost effective rainwater tanks are the plastic polyethylene tanks e.g. Jojo and Roto tanks. It is imperative that the tanks are opaque to prevent the exposure of stored water to sunlight, to eliminate the possibility of algal growth.

Very popular, modern looking galvanized tank.

Submerged ground rainwater tanks

Submerged rainwater tanks may also be used for retention of storm-water (water from roof and paved areas) for release at a later time, though this is not suitable for use in the home. Conventional rain water tanks are not designed simply to put underground and backfilled with soil. These will collapse and may pop out of the ground if empty. Special underground tanks are available from Jojo tanks otherwise a special underground room may be built with a concrete floor and roof with brick walls in which vertical tanks can be installed. If you don’t know what to do with that old pool that is consuming too much water and not being used anymore – convert it into a reservoir!

Water Tanks as Storage Devices

Water tanks are devices that store harvested rain water or run-off storm water or recycled grey water. This water will then be used at a later use, reducing one’s reliance for mains water both for economical and environmental reasons but especially to aid self-sufficiency.

Rain is really distilled water precipitating after condensing at high altitude where temperatures are low. It matters not whether water falling from the sky is rain, hail, sleet or snow, it is all water and may be harvested.

Uses of Water Tanks

Stored rain water may be used for irrigation, toilet flushing, washing machines (laundry and dishwashers, laundromats or private home owners), washing of cars (wash bays or private vehicles/office buildings), and also for drinking when filtered and treated adequately. In a nutshell – it can be used for any application, wherever you would’ve used normal municipal water. We can supply clients with a water analysis report as per the SANS drinking water quality after our filtration system has been installed.

Filtering of Water for Water Tank Storage

While all water tanks need to be sealed, to screen out mosquitoes, the lack of proper filtering or closed loop systems will create breeding grounds for mosquito larvae. With our bigger systems, especially for an off-the-grid system we start filtering the water at the gutter / downpipe already BEFORE it enters the water tank (s). This also prevents any blockages in the underground pipes and the breeding of mosquitoes.

If the harvested rain water is used for drinking, it should be filtered adequately. Filtration (such as reverse osmosis or ultra-filtration) will remove all pathogens. Other filtration consists of ozone and UV (ultra violet) treatment.

Certain paints and roofing materials may cause contamination. In particular, lead-based paints should never be used even as a primer onto metal surfaces. Tar-based coatings may affect the taste of the water. Chemically treated timbers and lead flashing should be excluded from roof catchments.

Maintenance of rainwater catchment areas includes regular removal of vegetation and debris from rain gutters. As long as a rainwater tank is kept closed to preclude light from entering, no algae will grow, so the only maintenance that needs to be done is perhaps removal of the sediment on the floor of the tank once a year.

Apart from rooftops, tanks may also be set up to collect rainwater from patios, driveways and other surfaces. This water though may only be used for irrigation and toilet flushing, as it may be soiled from pedestrian and other animal use.

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