Rainwater is generally safe to drink but collecting a good, clean supply depends on “low maintenance — not no maintenance” when it comes to water tanks & stored water.
Rainwater can provide a free and renewable supply of natural, soft, clear and odourless water for a range of purposes including drinking, food preparation, washing, bathing, laundry, toilet flushing and gardening.
Rainwater is a useful addition to mains water for many households. However, in some areas rainwater is the primary source of water for all household purposes.
Is rainwater safe to drink?
Generally rainwater is safe to drink. If the rainwater is clear, has little taste or smell and is from a well-maintained system, it is probably safe and unlikely to cause any illness for most users.
Disinfecting the water before consumption should be considered for those who are immuno-compromised such as the very young or very old, cancer patients, people with diabetes, organ transplant recipients or people who are HIV positive,. This can be achieved by bringing the rainwater to the boil.
Rainwater collected in rain water tanks generally contains few chemicals. However, there may be increased pollution by airborne contaminants from very heavy traffic or in industrial areas.
Collection of rainwater for human consumption (drinking and cooking) in areas affected by very heavy traffic, industry, incinerators and smelters is not recommended.
The microbiological quality of rainwater collected in domestic tanks may not be as good as mains water, but if collection systems are well maintained, the risk of harmful organisms being present is low.
Rainwater does not contain fluoride. Where rainwater is the major source of water for drinking and cooking, advice about alternative sources of fluoride should be sought from your local dentist, school or community dental service.
How can water quality be protected?
The supply of good quality water depends on ensuring correct design and installation followed by sensible maintenance of the rainwater tank and catchment area. The collection of rainwater involves “low maintenance — not no maintenance”.
The water tank
Water tanks are available in a wide range of materials including galvanised, AquaplateTM or zincalume® steel, concrete, fibreglass or plastic (various types of polyethylene). All these water tank materials can be suitable if the tanks have been manufactured specifically for the collection of rainwater. Some types of new water tanks may have to be washed or flushed before use. The manufacturer should be able to provide advice on whether this may be necessary.
When installed, the rainwater tank should be covered and every access point except the inlet and overflow should be sealed. The inlet should incorporate a mesh cover and a strainer to keep out debris and prevent the entry of mosquitoes and other insects. The overflow should also be covered with an insect-proof screen.
The catchment (roof)
In general, house and shed roofs are used as catchment areas. Rainwater can be collected from most types of roof, including asbestos roofs, providing they have not been painted with lead-based paints or coated with bitumen- based material. Some types of new tiles and freshly applied acrylic paints may affect the colour or taste of rainwater and the first few run-offs may need to be discarded. As a precaution, chemically treated timbers and lead flashing should not be used in roof catchments. Also, if possible, rainwater should not be collected from parts of roofs incorporating flues from wood burners.
Overflows or discharge pipes from roof mounted appliances such as evaporative air conditioners or hot water systems should not be allowed to discharge onto the roof catchment area or gutters.
First-flush devices can be used to prevent the first rains from flowing into the water tank after a dry period. This will reduce the amount of dust, bird droppings, leaves and debris that have accumulated on the roof from being washed into the tank. The use of these devices is recommended. Alternatively the tank inlet could be disconnected so that the first run-off of rain after a dry spell is not collected.
Roof catchments should be kept clean and clear of leaves and debris. Overhanging branches should be removed. Gutters should be regularly inspected and cleaned if necessary.
The use of screens/guards should be considered and all screens should be cleaned regularly.
Water ponding in gutters must be prevented as it can provide breeding sites for mosquitoes and could lead to eggs being washed into tanks. Tanks should not be allowed to become breeding sites for mosquitoes. If mosquitoes are detected in a tank, the entry point should be located and closed.
For most types of tanks mosquito breeding can be stopped by adding a teaspoon (5 mL) of domestic kerosene. However, kerosene should not be used in AquaplateTM or some plastic tanks. Prevention of mosquito access is the best control option in all cases.
Tanks should be examined for accumulation of sludge at least every 2-3 years. If sludge is covering the bottom of the tank it should be removed by siphon or by completely emptying and rinsing the tank. Professional tank cleaners are available in some areas. Excessive sludge is a sign of inadequate maintenance of the catchment area (roof and gutters).
Regular disinfection should not be necessary. If it is suspected that water in the water tank is contaminated, it can be disinfected using 40 mL of liquid sodium hypochlorite (12.5% available chlorine) or 7 grams of granular calcium hypochlorite per 1000 litres of water.
A chlorine taste and odour may persist for a few days but this does not make the water unsafe for drinking. Stabilised chlorine should not be used.
Size of water tanks
The size of tank required to provide the primary or total supply of household water will depend on a number of factors including the amount and pattern of rainfall, roof area and water usage.
Where rainwater is being used to supplement mains water, the size of tank is not such a critical issue and will depend on space, cost and user requirements (such as drinking, cooking, washing and watering the garden).
Source: South Australian Government
Although rainwater can be incredibly pure and contaminant free, the catchment areas are seldom perfectly free of debris and dust, etc. This is why we always recommend that rainwater be properly filtered if it is to be used for drinking purposes. The use of disinfectants such as chlorine ensures that most microorganisms are killed but studies have shown that the chlorine itself can be detrimental to one’s health in the long term. An appropriate filter should be installed to remove all traces of chlorine and other disinfectants that may be used. Rainwater has been shown to be much better for plant growth compared to chemical-laden municipal water; using rainwater instead of municipal water for your lawn and garden will begin to show benefits in a relatively short space of time.
Choosing a water tank is an important decision. In South Africa, high quality polyethylene or plastic water tanks are usually the most appropriate type of tank (easy to transport and install as well as relatively inexpensive compared to stainless steel tanks and concrete tanks). We recommend water tanks and other products made by JoJo Tanks (South Africa); JoJo water tanks are guaranteed for 5 years and are manufactured with a food-grade lining – important for keeping your water fresher for longer. Click on the links below to see the wide range of JoJo Tanks products available, including water tanks, rainwater tanks, slimline tanks, tank stands and septic tanks.
JoJo Tanks South Africa offer a wide range of plastic water tanks and chemical tanks to suit every household, business or agricultural need, including silo tanks and silo tank stands. See JoJo Tanks VERTICAL TANKS, HORIZONTAL TANKS (transporter tanks), STEEL TANK STANDS and OTHER JOJO PRODUCTS. Also see JoJo Tanks’ NEW 6000 LITRE UNDERGROUND TANKS. Also see our FAQ and WATER TANK PRICES.
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We are authorised JoJo Tanks dealers in South Africa and dispatch orders directly from JoJo Tank depots to save on transport costs. Full range of JoJo Tanks products and JoJo water tanks for sale. CONTACT US for a quote on the right JoJo water tank or other JoJo product for you. Special discounts are available on multiple orders of chemical tanks and water tanks and to our commercial and government customers.
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Live in the USA and need rainwater harvesting equipment? Click HERE!