I have noticed for the past couple of months that on occasion when filling the bathtub, the water looks rusty. This brownish color does not happen every time the bathtub is filled, but is now happening more often. Is this a sign that my hot water heater is on the way out? A friend once told me that if you drain the tank on the heater a let it set for 24 hours and refill, the water coloration will stop. Have any of you guys experienced this before? A new heater is a sizable expense so I would appreciate any advise before moving forward.