Backup in a Box Mains Water Backup

£215.00 ex VAT

Rain Backup in a Box® [SD] for shallow dig tanks – the plug-and-play mains water backup for rainwater harvesting systems. When the rainwater runs out this simple controller will top up your tank to a minimum level with mains water – safely and economically. Another eco-innovation manufactured by Rainwater Harvesting Limited.

SKU: RWH-BUB02 Category:


Rain Backup in a Box® [SD] for shallow dig tanks – the plug-and-play mains water backup for rainwater harvesting systems.

Rainwater harvesting plays a large role in reducing the dependence of any building on expensive treated water from the mains. Toilet flushing, clothes washing and any outdoor use of water can be assured by rainwater. In most cases the total mains use of the building can be cut in half.

But what about in time of drought?

Every system needs a mains water backup to keep the appliances going. The simplest way is a float switch and solenoid valve; the float switch detects when the rainwater storage tank is empty and opens the electrically-activated solenoid valve so that mains water flows into the bottom of the tank. When the float switch floats off the bottom of the tank it turns the solenoid valve off. The bulk of the storage tank remains empty ready to admit the water from the next rain shower.Water flow from a Rain Backup in a Box

U.K. Building Regulations require that rainwater cannot possibly flow back into the mains water supply. For this reason all mains backup devices must have an air gap where the mains water flows into the rainwater tank. The simplest way to do this is for the mains water to flow through open air into a funnel shaped device called a tundish. It can be seen in the photo at the bottom right of the unit.

The Rain Backup in a Box® is fitted inside the building where the occupiers can see and hear it. When rainwater has run out, any mains water running from the solenoid valve into the tundish can be seen through the transparent cover and can be heard through the aperture at the side.The Rain Backup in a Box® replaces a higgle piggle of components with a single wall mounted unit, one electric plug to a wall socket, mains water input and a pipe to the underground storage tank.

Limitation on Use: Note that the Rain Backup in a Box® is intended for domestic and light garden use. If you run two garden taps with a high power pump (like the HydroForce, Steel Pumps or Divertron pumps) then the outflow of water is higher than the inflow from the backup device.

When the underground storage tank is empty the pump will have no water and its dry-run-protection will turn it off. Some pumps need resetting at the main in this case which is a bore. Most users get round this issue by having mains water taps available alongside the rainwater outlet so that they can switch to mains for garden use when the underground tank is empty. The Rain Backup in a Box® will continue to keep up with demand in the house for toilets and washing machine