Inlet Check Valves (ICVs) are used to help prevent wellback and spitback.
Wellback occurs when fuel in the tank expands during the heat of the day, and moves up into the fuel fill hose, possibly overflowing into the water.
Wellback does not occur during fueling.

These spring-loaded valves are installed in the top of the fuel tank, and are normally closed thus preventing fuel from moving up the fuel fill hose.
During fueling, the weight of the gasoline opens the valve, so fuel can enter the tank.
All Perko inlet check valves are designed to handle incoming fuel flows in excess of 18 gallons per minute.

Mounting options for ICVs include flanged (for plastic tanks), threaded or welded (for metal tanks), and swivel (for both plastic and metal tanks).
The gasket is not included on flanged valves.
Threaded valves mount with a 1-1/2" NPTF thread.
Swivel valves include valve, valve housing, O-ring, snap ring, and tank insert.
Custom ICVs are also available for specialized applications.
There is a version of fuel inlet check valve which can be inserted into the bottom of the fuel fill hose, allowing for use of a standard fuel tank inlet fitting; see Related Products, below.


Heavy on the technical side...
Maximum fuel leakage is 0.5 cc/min @ 12.5 kPa and 149 kPa