How Do I Stop Deer From Eating My Flowers

May 12,  · The recommended dose for treating drinking water is 2·5ml per 5 litres. If you look at the Milton website you will see that they recommend, in the camping and caravanning section on the hygiene tab, a dose rate of 15ml per gallon (call that 5 litres) for sterilising water tanks, then draining and flushing after 30 minutes.