At Highland's current Rates the cost of 1 Gallon of water is a little more than ½ of a penny ($.0055). Accordingly, completely flushing a 50 gallon water tank costs little more than Quarter ($.25) . Additionally, customers tend to overestimate how much water they had to let run to clear their water. The true costs are most likely between a Quarter and a Dollar. We always regret such occasional inconveniences, but credit is not issued in such cases.