Rule 500GPH Standard Bilge Pump - 12V500GPH Standard Bilge Pump 12V Customers talk about flow, they want the water out of the bilge, and fast. Improved design and performance means that our next generation 500GPH pump will produce this flow at just 12V rather than 13. 6V as previously required more typical of on board voltage supply. Our next generation of Rule pumps include check valves and to do this, we've created hidden air vent to prevent airlocking. Under each strainer tab there is