The solenoid valve in the Backup in a Box has a flow restrictor limiting the flow rate to 4 litres per minute. This means that you have a trickle of water moving through the unit to ensure that the water can escape through the outlet. If water is backing up the outlet pipe and overflowing through the 1 inch airgap at the back of the control panel or through the overflow pipe please check the following :

• Check that there is a 300mm vertical drop from the bottom of the unit to the first bend in the pipework. If there isn’t then you will need to raise the unit to ensure this is the case.
• Ensure that there is sufficient fall from the frst elbow to the underground tank, either directly through a service pipe to the tank or via a nearby downpipe.

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