This is everything that your plumber will require to assemble a "Manual Town Tank Switching" unit. The unit is installed and connected to the town mains water supply, the Grundfos pump drawing water from your tank and, the house. When you have rainwater in your tank, the tank valve is open and the town mains valve is closed and you are operating on rainwater. If you run out of rainwater in the tank, close the tank valve and open the town mains valve - it is that simple. We supply this equipment as individual "Watermark Approved" components so that your licensed plumber can assemble them and install the unit to comply with all regulations. "Back flow prevention" is carried out by the dual check valves and these also prevent town mains entering your tank and, tank water entering the mains. For further details and a larger image, click on the "information" button to the right.