90 Degree P-Trap Fuel Tank vents help prevent water from entering the fuel tank, yet allow air to vent freely, during normal sea conditions and washdowns. This eliminates the need for an anti-siphon loop in the vent hose. For 5/8 inch I.D. hose. Meets ABYC Standard. The arrows in this cross-section show the baffled route that water would have to travel in order to reach the fuel vent hose.