The Davey Rainbank and Onga Water Switch automatically switch to mains water supply when you have used the water from your eco sac®. When it rains again and your eco sac® collects rainwater, the Davey Rainbank and Onga Waterswitch sense the stored rainwater and uses the water from your eco sac®. In our ESM range, we include a mainswater controller as well as a float chamber to connect the Rainbank to the eco sac® so that the Rainbank can detect when the sac is nearly empty. The float chambers can also be bought separately.