Petersons Supplies BWVALVE100MMPTRAP - Back Water Valve with P-Trap, 100mm (4") Ball-Type

The Petersons Back Water Valve with P-Trap is a drainage assembly for vaults, basements and similar below-grade spaces. Petersons Supplies states that its backwater valves use ball technology that allows stormwater to exit the vault or basement, while the P-trap prevents gases from coming back through the system.

• Backwater (backflow prevention) valve combined with a P-trap
• Ball-type closure mechanism
• Connects to a 4" (100 mm) exit pipe
• Intended for stormwater drainage from vaults and basements

A valve of this type is installed in the outgoing drain line so that normal flow passes outward while reverse flow from a surcharged sewer or storm drain is blocked. Combining the valve with a P-trap in one assembly maintains a water seal in the line, which is what keeps sewer gas out of the occupied space. The seller describes the item as shipping as one each consisting of two parts (grey and white); that packaging detail is not stated on the manufacturer's product page and should be confirmed before ordering.