Drainage

Drainage for backflow prevention assemblies shall be provided for all installations of DCVA or RPZA to

accommodate discharge during testing or draining of the unit and for RPZA relief valve discharges, as follows:

· For RPZA devices, drainage capacity shall be sized to accommodate both intermittent discharges and a catastrophic failure of the relief valve. Refer to manufacturers flow curves to determine maximum discharge rate based on supply pressure or on-site pressure; whichever is greater.

· Discharge from relief valves must be readily detectable to maintenance personnel either visually or by means of water level alarms, flow indicator lights, etc.

· All drainage from RPZA's must be by gravity drains. Sump pumps are not allowed unless they are sized to accommodate the maximum discharge rate and connected to emergency power supplies.

· An air gap must be maintained between the RPZA relief valve opening and any discharge piping. The air gap must be at least twice the dimension of the effective opening of the relief valve; but in no case less than 1 inch.

· Manufacturer's air gap fittings may be utilized provided that they maintain a proper air gap and do not enclose or cover the relief valve. These fittings are only sized to handle intermittent and low flow discharges. Additional drainage capacity may be required to accommodate a catastrophic relief valve failure.

· Discharge piping from relief valves shall be terminated a minimum of one inch above any floor drain or other receiving receptacle.

· Discharge piping connected to a storm sewer shall be equipped with backwater check valve.

· Discharge piping connected to a sanitary sewer shall be trapped and equipped with a backwater check valve.

· Discharge piping from pits or other structures must be terminated above grade in an area not subject to flooding (generally one foot above the 100 year flood elevation). The terminal end of the discharge piping must have a rodent screen and may need to be supported by a headwall. Flap valves should also be considered to prevent entry of cold air.

· All exterior drains shall be kept free of snow during winter.