Anti siphon valve

[Yamahaha]

I am in the process of installing a new 60 gal fuel tank, feeding a '04 Yamaha F150. The pickup tube is plastic, connected to a alum fitting. What's the deal with the anti-siphon valve other than CG regs. One mechanic told me that the valve can restrict the gas just enough to affect the performance of the fuel pumps.

 

[rodbolt]

Re: Anti siphon valve

coast guard says that if any portion of the fuel system drops below the level of the tank it must have an anti-siphon valve. however the valves are made in many opening pressures. the coasties even wrote the formula to address how much pressure it opens at based on the distance from the top of the tank to the lowest part of the fuel system. if you can design the system so that nothing drops below the tank level an antisiphon valve is not required.