Do NOT under any circumstances put water in that tank.. Find a pump sprayer, the kind that has a hand pump on top and a hose with a wand. Make shure it is clean and put DIESEL FUEL in it.. Adjust the nozzle to mist and put the wand up the drain plug hole in the bottom of the tank and wash out the whole inside of the tank letting the fuel to wash out into a pan.. This should take out any leftover chlorine in the tank..