Guidance on use of rainwater tanks

Tank desludging

Page last updated: March 2011

All tanks should be examined for the accumulation of sediments every 2-3 years, or if sediment is evident in the water flow. As discussed in Section 4, accumulated sediments can be a source of chemical contamination and off-tastes and odours.

Sludge can be removed by siphoning without emptying the tank. To do this, use an inverted funnel in the end of a hose and move it carefully across the bottom of the tank. The sludge, plus the lower portion of water in the tank, can be released to waste. If leaves and coarser debris are present in the sludge, a siphon hose of approximately 50 mm diameter should be used.

Sludge may also be pumped from the tank with minimum loss of water by using a suitable motor-operated pump and attachments.

Finally, sludge can also be removed by draining and cleaning the tank. If a drain plug is provided at the base of the tank, water can be run to waste to discharge the sludge. Once the tank is empty, the remaining sludge can be scooped up and removed through the access opening. Care should be taken not to disturb the protective film on the inside surface of the tank.

Tank cleaning businesses (generally listed in telephone directories) may also be available to desludge tanks.

Organic material removed from the tank may be disposed of in the garden by spreading and digging into garden beds. Environment protection agencies should be consulted about off-site disposal.