Master Plumber Backflow Preventer – Brass – 4″

Protect your home from backwater flooding with this Master Plumber antiflooding device for 4-inch diameter drains. The brass flood guard allows water to flow normally through the drain until the sewer backs up. It then arises to seal off the backwater until the water recedes. 1 unit per package.

• Operates like a check valve to seal off water back-up caused by overloaded sewers
• Water flows normally through the drain until sewer begins to backs up