Hello smart folks, I have a question. I have an unused never filled with fuel, fuel tank. My last trip we ran out of the 1000 gallons of water (water is only used for wash down, showers, toilets and ice maker for icing beer, water and fish down) Not For Drinking!!! Can I use this tank for added water capacity with out messing up the water supply and without damaging the future fuel usage for the tank? Thanks Paul