Most rainwater harvesting systems require a means of switching to an alternative source, in the event of the system running out of rainwater. However, there are strict regulations governing the way that this is done, in order to eliminate any risk of non-potable water being able to siphon back into the mains supply. This is achieved through the use of an air gap that the mains water must pass through before entering the tank. Our special mains water top-up units are designed specifically for this purpose.
For direct systems, where the mains water is fed to the rainwater tank itself, we supply a special assembly that incorporates a tundish. This provides the necessary air gap to comply with regulations, but means that the water flowing out of the tundish is no longer under pressure and must rely on gravity to reach its destination. For this reason the assembly must be at a level higher than the top of the tank that it is supplying; it must also be located indoors.
The water supply into the tundish is regulated by a solenoid valve which is connected electrically to a float switch. As the water level in the tank falls, the float switch drops and opens the solenoid, thus allowing the mains water to pass through the tundish into a pipe, which then leads back to the tank. As the tank water level rises again, the float switch lifts and shuts off the solenoid. When used with our precision float switches, the amount of mains water used in this way is kept to a minimum.
Each assembly also includes a flexible braided connecting hose for ease of installation, and an isolating valve with integral dirt strainer to protect the solenoid valve from any foreign matter. The stainless steel tundish incorporates a laminar flow device to ensure that a vertical splash-free column of water passes through.
These mains top up units can also be used in indirect systems for filling a header or break tank in the same way.
Five models are available, to fit following pipe sizes: 1/2″, 3/4″, 1″, 11/2″ and 2″