Scotland Island has a number of water-related issues. The island is not connected to mains water  or the city sewerage system (those services delivered by Sydney Water in most of Sydney). This means that we have unique conditions which entail some careful management and knowledge of local conditions.

The average house has 136,000 litres of rainwater per annum deposited on its roof. Even in a dry year, it will be over 100,000 litres. Collecting this water for your water tank is one of the challenges. Here are some tips to help.

Collecting water

It is important to maintain your rainwater tank and components so they work effectively and reduce the risk of water contamination. Preventing problems before they arise will save you time, money and water. A few simple measures will keep your collection system clean, drinking water pure and sweet.


  • Clean water starts with a clean roof, so sweep your roof before any predicted rain.
  • Warning: Roofs can be very slippery when they are wet, and children should never be allowed on roofs. Your safety is an important consideration before getting on your roof. 


  • Keep gutters clean of dirt and leaf litter and plug any leaks.
  • The best gutters for collecting clean water are 150 mm half-round supported from underneath. Overstraps make cleaning difficult.


  • Keep downpipe system simple with a minimal number of bends.
  • Create a simple way of deflecting water away from catchment tanks to avoid collecting dirty water if roof and gutters have not been cleaned.

First flush devices

  • Use first flush devices to prevent the first rains from flowing into the tank after a dry period. This will reduce the amount of dust, bird droppings and other debris that have accumulated on the roof.
  • An alternative to a first flush device is to manually disconnect the tank inlet so that the first run-off is not collected, or to divert the water away from the collecting tank.


  • Keep vegetation out of water supply with a simple filter at the base of the downpipe or at tank inlet. An effective system which fits into your downpipe with a larger grid to stop leaves, twigs, bark, etc and a fine mesh to block remainder. Some people use stockings as a filter.
  • Clean filters after the first good downpour has cleaned your roof and gutters.


  • Optimally, your tanks should have at least a 40,000 litres capacity. While this is now a Council requirement for any new Development Application some properties do not have that volume of storage.
  • It is best to have  two tanks – a smaller collection/settlement tank and one or two  storage/header tan.ks
  • Note that a gravity supply instead of pump pressure supply is likely to reduce  water usage, particularly in showers.
  • Clean your tank regularly. There are different means to do so. Safety is a key consideration here and if you plan to go into your tank. You will need to consider the size of the opening, ease of getting in and out and the presence of sufficient oxygen,  A tank is considered a confined space.  Some tanks with a lot of deposits can have low oxygen levels as organic matter creates carbon dioxide and other gases when decomposing .  


Research has shown that mosquitoes have a limited range, so if you have a lot of mosquitoes, it may be because of inadequate screening or water management in your property or in neighbouring properties.

Do your bit to reduce compulsory blood donations and possible infections by screening all inlets and outlets to your tank, including the overflow pipe. Also, have a look around outside and remove any containers that could collect water, such as trays around pot plants.

  • Check gutters regularly to prevent ponding of water where mosquitoes can breed.
  • To prevent tanks from becoming breeding sites, the first step is to make sure the tank is fully closed with no gaps allowing for mosquitoes to enter.  Fine sieves can be placed at outflow holes 
  • Use light, flexible screening (available from some garden shops) to cover collecting tanks and other water containers where mosquitoes can breed.
  • More information:

Organic matter in your tank

  • Once the Spotted Gum bark starts to fall towards the end of the year, rain water tanks can very quickly become tainted with organic matter.
  • Too much organic matter in the tank can cause problems. As the water warms up in the hottest months, it creates the perfect growing conditions for unwanted life forms.
  • Be diligent in cleaning your roof and gutters at this time. If you have overhanging trees or do not collect water from your roof, wait until bark-shedding season is over.
  • One technique for keeping your tank water aerated is to use a fish tank aerator. They are available with a solar panel so that they can run continuously. The Fish Works Pond Shop in Terrey Hills is one nearby supplier. 

Emergency Water Supply

  • The SIRA water supply lines can be used to fill your water tanks with non-potable Sydney Water that is piped from Church Point.
  • Bookings MUST be made prior to filling. Using the system without a valid booking is theft.

Please read about the Emergency Water system here.