Water Tank Secrets » Water Tank Hazards

Mosquitoes in Water Tanks

admin — Wed, 18 Nov 2009 13:55:45 +0000

Rainwater tanks can provide very good habitats for mosquito breeding. The most effective control measure is to prevent access of adult mosquitoes. If access has occurred remedial action can be taken to prevent the release of mosquitoes.

To prevent mosquito breeding and contamination, its vital guttering and pipework should be self-draining or fitted with drainage points.

Ensure that unless in use all access points excluding the inlet and any overflows are kept shut with close fitting lids that will prevent access of mosquitoes.

Inlets and overflows should be covered with closely fitting removable insect-proof screens. The screens should be made of non-rust material formed, typically, with 0.315 mm diameter material and 6×7 mesh openings per cm2. The screens should be readily accessible for regular cleaning.

Water should not be allowed to pool under the overflow outlet or tap of the tank as these can become mosquito breeding sites. The tank should be a sealed unit with the lid preventing sunlight from reaching the water. Sunlight encourages the growth of algae that may taint the water.
A good tank design prohibits vermin from entering the tank by ensuring all the inlets are covered with screening too small to allow them in, however holes and spaces created by you after or during installation could allow mosquitoes to enter, so be careful.

Mosquito larvae (wrigglers) found in rainwater tanks indicate the presence of an opening through which the female mosquito can enter and lay eggs on the water. The opening should be closed. This will prevent further entry and will also prevent the escape of any hatched mosquitoes.

Larvae present in rainwater can be treated by the addition of a small quantity of domestic kerosene (5 mL per 1000 litres). Commercial or industrial kerosenes (eg power kerosene for tractors etc) should not be used for mosquito control.

Kerosene should not be used in tanks coated with AquaplateTM. In addition, kerosene may not be suitable for use in tanks constructed or lined with plastic. If in doubt consult the manufacturer.

Used carefully kerosene will not provide any risk to human health but excessive amounts can taint the water and it is a human poison. Kerosene should not be added when water levels are low. Kerosene added to the surface will not mix through the body of rainwater in the tank and it will either be washed out of the tank by overflow or it will evaporate.

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Dead Animal in the Water Tank

admin — Wed, 18 Nov 2009 13:54:41 +0000

Dead Animals present a health risk when they come in contact with rainwater in a water tank.

Where a rainwater tank has become contaminated by a dead animal such as a bird or rodent, carefully remove as much as possible of the animal carcass and then disinfect the water.

If the animal is large such as a possum or cat and badly decayed, the taste of the water will probably be affected. It is recommended that the tank be drained and cleaned as soon as possible.

It is also vitally important that the point of entry for the animal should be located and repaired/sealed.

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Water Tanks and an Asbestos Roof

admin — Wed, 18 Nov 2009 13:52:31 +0000

Although no longer used in new houses, asbestos in a cement matrix may be present in some older type roofs (pre 1970s). Although asbestos fibers are dangerous to health when inhaled in sufficient quantities, it is not believed that asbestos in drinking water poses a risk.

Asbestos fibres have been detected in drinking water throughout the world with no known health effects.

Roofing material should be left undisturbed as far as practicable since asbestos fibres, while bound securely in fibro-cement sheeting, can be released into the air by actions such as cutting, grinding or drilling. High pressure roof cleaning methods should also be avoided.

Where the roof catchment area has deteriorated badly it should be replaced with asbestos-free substitutes.

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