Better check your state laws, gravity flow in some States are not OK. I have a pump and egg timer on mine, 50gal under the tool. Also you should think about a fuel filter on it, too. I have had mine on for over two years, help when on a long trip and you use the GASBUDDY.com to find cheap fuel. I jsut go off the mileage, know I can run about 550-600 miles on the back tank.