New research revealed unsealed and damaged rainwater tanks could expose millions of Australians to the risk of mosquito-borne infectious diseases like dengue fever. So how can you keep your tank safe?
water tank in garden

Nobody wants insect larvae in their water. A working mozzie mesh is an easy way to keep these pests out and your water clean.

Rainwater tanks are a great alternative water supply and can help save you some cash, especially during times of water restrictions. But they can also become breeding grounds for mozzies that can carry all sorts of nasty infectious diseases, including dengue fever.

The Aedes aegypti mosquito infects hundreds of millions of people across the globe each year with dengue, Zika, chikungunya and yellow fever.

You might think of these as being diseases confined to the tropics. But new research has found the mosquito in a number of towns in the Wide Bay region, closer to Brisbane.

An aedes aegypti mosquito. Image: Muhammad Mahdi Karim
An aedes aegypti mosquito. Image: Muhammad Mahdi Karim

An aedes aegypti mosquito. Image: Muhammad Mahdi Karim

Our vector ecologist Dr Brendan Trewin was one of the lead researchers on this study. Brendan studies insects that transmit pathogens and their contact with humans so we can better understand how diseases spread.

“Previous studies had suggested that conditions in Brisbane were inhospitable for the species during winter, but our findings show that rainwater tanks could provide year-long protection for the Aedes aegypti mosquito in Brisbane and other sub-tropical areas of Australia,” Brendan said.

It is believed that more than 40 per cent of Brisbane properties now have rainwater tanks, though this number could be much higher as there is no formal registration or monitoring procedure.

“The last time Brisbane had significant Aedes aegypti and dengue epidemics they also had a lot of unsealed rainwater tanks, and our research suggests it was the decision to remove these tanks in the 1950s that was one of the keys to driving the disease-carrying mosquito out of the city,” Brendan said.

Our researchers measured mosquito survival and development during simulated Brisbane winter conditions in rainwater tanks and buckets and found that 70 per cent of mosquito larvae survived to adult hood in water tanks, and 50 per cent in buckets.

Now, we’re not suggesting you should ditch your rainwater tank, but it’s important to be aware that if your rainwater tanks are not maintained properly, they could become a breeding ground for mozzies bringing with them potentially serious implications for Australian public health. And you might be unknowingly adding to the risk if you make modifications to your tank like removing the sieve that collects leaves from the roof and gutters, or adding modified downpipes.

Rainwater tank with damage to the top seive.

Damaged mesh is as good as no mesh at all.

As Australia’s national science agency, we’re working on a range of tools to help safeguard Australia, from real time alert systems; quicker and smarter diagnostic tools; right through to sterilisation technology that eradicates the mosquito.

So what can you do to mosquito proof your tank?

  • Check there are sieves at the entrance and overflow and there are no gaps
  • Check for cracks in plastic tanks
  • Make sure the sieves aren’t rusting and there are no holes
  • Mosquitos feed on broken down leaves so keep gutters leaf free
  • Check that first flush devices are draining


  1. When a sealed rainwater system is required how is the gutter to downpipe effectively screened?

    1. Hi Don,

      There are a number of ways you can prevent leaves and other nasties building up in your gutters. The first way it to have your gutter screened with Gutter Guard or a similar product. There are also rainwater tank diverters which will take leaves out of a downpipe and divert them to the ground while the water continues through to the tank.


  2. What about older tanks with the corrugated tin roof? Lots of openings and difficult to seal.

    1. Hi Jeff,

      Sorry for the delay in answering your question. If a tank has rusted through then it is non-compliant with regulations in Queensland and must be removed. Elsewhere in Australia it will fall to local government rules but unsealed tanks are a public health risk to invasive and disease spreading mosquitoes and should be sealed or removed.


      1. Hey Brendan, I think he’s talking about the gaps between the roof and the tank itself. Similarly to the apex of a corrugated tin roof, there is a gap between the top of the ‘tank’ and the corrugations in the roofing material. I’ve just had a corrugated tank installed and there is 10mm (at least) gaps all around the join of the tank and roof where the corrugations are.

  3. I believe using paraffin is a better method of ‘sealing’ the surface to prevent larvae from breathing but it does need to be replaced after every ‘overflow’ event to maintain the film.

  4. What about a few drops of kerosene to stop mosie lava breathing

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