I've drained stuff that won't even light. Bought an 80 gallon DeeZee transport tank a few years back. Still had forty gallon of fuel in it(this was when diesel was high). Cost me a set of filters. Drained it out and it wouldn't even burn.
My dad got some 'free' diesel from the lumber mill where he works... He borrowed my backhoe, and then called and said it lost power, then died. We must've drained 15 gallons of water from the 30 gallon tank. It took a bunch of fuel filters and dicking around before we finally got all the water out of the fuel system.