Cleaning Your Rainwater Tank

Cleaning Your Rainwater Tank:

In a similar way that all drinking water is regularly maintained and cleaned, the same applies for rainwater tanks and systems. If you own a water tank, then you probably already know that they require a certain amount of upkeep to ensure that the tank is operating at the optimal level and the water you are getting from it is of a high quality.

With the recent extreme weather and climatic events felt across the country, larger amounts of sediment and waste has been making its way into water tanks. Bushfires and dust storms caused by the ongoing drought has resulted in higher amounts of dust and ash in the air, which in turn gets into the flow of water into rainwater tanks. Over time, sediment from leaves, dust, debris and ash can build up on the bottom of tanks and begin to decompose into a sludge substance. Sludge build ups can result in bacteria to spread in the water supply, which if consumed can cause serious health issues.

It is recommended you clean your tank at the end of summer when water levels are at their lowest. Make sure you turn your power off when doing it yourself if you have an electric pump (also pull plug as electricity can still flow). Use the remaining water in your tank around your garden, pool, car to make good use of it. Then run some fresh water from your garden hose through the tank inlet to flush out any remaining dirty water. Keep doing this until the water coming out of the outlet runs clear. Reasonably high pressure water is best as it can easily remove any debris on the side of the tank.

To remove sludge without losing the rainwater you’ve already caught, you must pump out the organic material lying on the bottom using a tube inserted through the tank inlet. Many professional tank cleaning services are available. If you’re going to get into your tank are do it yourself, note that there are some dangers that go with this including working in confined spaces.

One way to mitigate the build up of sludge is the use of First-Flush Diverters. A first flush diverter (also known as a roof washer) is a simple contraption that diverts the first flow of water away from a rainwater catchment system. The first pass of water in any storm essentially washes your roof of all the sediments that have collected since the last rain. The use of leaf strainers and UV filters are also a highly effective means of keeping tanks clean.

You may find that windblown ash, debris, dead animals or fire retardants have affected your rainwater tank when returning home after a bushfire, storm or dust storm. The first rainfall after a fire should be run to waste, if the roof has not been cleaned. Clean your roof to remove ash and debris, if this can be done safely. Check your roof and guttering for dead animals and remove if present. Water testing is usually not necessary, as contamination is usually obvious. If the water is contaminated the tank should be drained, cleaned and refilled. Working inside a tank can be very dangerous. Professional tank cleaners are available in some areas. Filters and other water treatment equipment could be affected by debris. Refer to the manuals for your equipment or seek advice from the supplier on responding to problems. After drinking water has been captured or delivered, flush taps in the property to bring through the new clean water from the tank.

How long does a water storage tank last?

A water storage tank can last up to 25 years or more if the correct maintenance procedures are followed. A Bushmans Poly water tank comes with a 10-year guarantee, while Industrial tanks come with a 5-year guarantee. 

The Australian Department of Health recommends once a rainwater tank is installed, the following components of the roof catchment and tank are to be inspected and cleaned at least every six months:

  • Gutters – they generally will need cleaning as well as inspection. If inspection finds large amounts of leaf material or other debris, then the inspection and cleaning frequency may need to be increased.
  • Roof – check for the presence of accumulated debris including leaf and other plant material. Accumulated material should be cleared. If tree growth has led to overhanging branches these should be pruned.
  • Tank inlets, insect-proofing and leaf filters – if necessary, these should be cleaned and repaired.
  • Tank and tank roof – check structural integrity of the tank including the roof and access cover. Any holes or gaps should be repaired.
  • Internal inspection – check for evidence of access by animals, birds or insects including the presence of mosquito larvae. If present, identify and close access points. If there is any evidence of algal growth (green growth or scum on or in the water), find and close points of light entry.
  • Rainwater tanks can become a significant mosquito breeding site when they are no longer required. Tanks that are no longer required should be drained, cut up and removed to an appropriate waste disposal site.
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