SAI Global’s Rainwater Tank Design and Installation Handbook states: ‘a… non-return valve on the outlet from the tank overflow is required before connecting to the storm water drainage system.’
The watertight overflow flap valve prevents vermin and backflow entering the water tank and polluting the rain water.
This water quality protection requirement is a standard that tanks from Sydney Water Tanks feature. The flap valve is available for 90mm, 100mm and 150mm pipes and is a full flow valve that does not restrict the overflow.
The alternative method of using a mesh screen on the overflow to prevent vermin entering the tank can become clogged with fine debris, and needs to be approximately twice the size to maintain the same flow.
A mesh screen will not stop contaminated water flowing back into the tank. Sydney Water Tanks watertight overflow flap valve will do that.
Many water tanks are supplied with open outlet points, leaving it up to the builder and plumber to find a solution.
Sydney Water Tanks with an overflow flap valve provides the clients with safe rain water and prevents expensive remedial work to clean out polluted tanks.
Every Sydney Water Tank is individually wet cast from 40mpa steel fibre reinforced concrete under a quality assurance scheme to ensure each tank complies with the quality requirements of AS1546.1.