HMWPE Flap Valves

It mounts at the end of a stormwater pipe or outfall. Water flows out through the hinged flap, and when the water outside rises from tide, surge or high water, the flap closes so it can’t flow back into the system. No power or operator needed. You’ll also hear them called flap gates, tide gates or outfall check valves.

No. A flap valve mounts at the open end of a stormwater pipe or outfall. A backwater valve goes in-line in a building sewer to keep a surcharged sewer from backing up into the building.

Use a wall mount (FV) when the pipe ends at a flat wall, headwall or chamber. Use a spigot mount (FVS) when you’re connecting to the pipe end itself, such as a retrofit on an open pipe.

Wall mounts need the matching FVMS mounting set (stainless bolts and chemical anchors). Spigot mounts need a Fernco Strong Back RC coupling sized to the pipe OD. Both are sold separately. See the part tables above.

Have the pipe OD, ID and material ready. Some sizes 14″ and up come in two versions, typically -1 for iron pipe size (IPS) and -2 for ductile iron pipe size (DIPS). With the right Strong Back RC coupling, spigot mounts connect to pipe such as PVC, HDPE, corrugated polyethylene, ductile iron, cast iron, steel, concrete and clay. Reach out and Fernco will confirm the valve and coupling.

Wall or spigot mount, nominal size, quantity and project location (city and state). For a wall mount, add the mounting surface and the space available at the outfall or headwall. For a spigot mount, add the pipe OD, ID and material.

Through Fernco’s authorized distributors and wholesalers. Fernco can coordinate the order through a local dealer, or you can buy through your preferred Fernco distributor. Find where to buy.

Not until the outside level drops. While the water outside is higher than the water in the pipe, the flap stays closed to keep backflow out, so account for this in your drainage design.

No. They’re for gravity drainage only. Working pressure is 10.75 psi (25 ft of head), and the recommended max temperature is 120°F constant, 180°F intermittent.

The HMWPE body won’t rust, pit or seize, and the counterweight and hardware are marine-grade 316 stainless. HMWPE is built for outdoor exposure, debris strikes and ice loading.

Fernco recommends an inspection after install and the first significant rain, then twice a year (spring and fall), after major storms or flooding, and more often where debris or sediment builds up. Clear the flap, hinge area and sealing surface, and make sure the flap opens freely and closes fully.

It depends on temperature: about 5 minutes at 69°F to 86°F, 20 minutes at 51°F to 68°F, and up to 30 hours at 5°F to 14°F. The installation instructions have the full chart, drill sizes and torque.

Reach out. Tell us the pipe size, material and site details, and ask about custom sizes.

Not at this time. In North America, Fernco Water Management starts with HMWPE flap valves. Fernco UK’s Water Management range also includes penstocks and orifice plates. If you’ve seen one of those and have a project for it, reach out and let us know. Your interest helps shape what we bring here.