If rumbling and crackling sounds are made by the water heater or there never seems to be enough hot water, it's time to clean the tank. This condition occurs when layers of sediment (caused primarily by hard water) buildup on the tank bottom and heating surfaces, producing a heat retarding scale. Mag-Erad is a patented food grade compound designed to dissolve and remove the hard water sediment through the heater drain. Mag-Erad is a plumber's product, safe enough for consumer use.