Mainline® 4″ Automatic Backwater Valve

Product Description and Features

The ML-FR4 ABS Automatic Backwater Valve is a great choice for retrofit situations where you have a limited amount of slope to work with. This is a normally-open design, automatic backwater valve that permits the free circulation of air throughout the plumbing system allowing gases to move just as if the valve wasn’t even there. The valve will close automatically when sewage backup occurs, reducing the risk of sewage backflow throughout the dwelling. The ML-FR4 is designed to be installed in building main lines to prevent backup through floor drains, shower drains, toilets and sink drains. It closes automatically when the municipal sewer line or septic system starts to back-up or a reverse flow occurs. The clear plastic lid allows for easy visual inspection and accessibility for cleaning. The design doesn’t restrict the withdrawal of a sewer snake since the gate remains in the open position, except when a backflow is in progress. The ML-FR4 drops 1/2″ from inlet to outlet over its 12″ installed length and is the outside diameter (male) of 4″ Schedule 40 ABS on both ends making it easy to fit either end into a female coupling or neoprene rubber with stainless steel clamp (Fernco brand type) adapter.

• Mainline Full Port Backwater Valve Brochure