Discoloured or rusty hot water

The colour narrows the cause. Rusty brown or red water from the hot side points at corrosion inside the tank, which the sacrificial anode exists to prevent: when the anode is consumed, the tank steel starts to give instead. Dark or black water can be manganese or sulphide-related sediment, and milky or cloudy water that clears from the bottom of a glass is usually air, not contamination.

The timing matters as much as the colour: a short burst of rusty water after the hot water has sat overnight is common in older galvanized or steel systems and can be the pipes rather than the tank. Continuous rusty water, or rusty cold water too, points outside the heater.

Manufacturers specify periodic anode inspection, and a depleted anode is the most common reason a tank starts to rust from the inside. In Metro Vancouver's very soft water the anode can be consumed faster than in hard water because soft water is more aggressive to the tank's steel, which is why anode checks matter more here than descaling.

Replacing a depleted anode is routine while the tank is otherwise sound; ignoring it leads to tank corrosion and a leak that ends the tank. A technician measures what is left of the rod at the service visit rather than guessing by age.

Rusty water itself is not an emergency, but it is a warning. If the hot water turns rusty and the tank begins to weep or leak, the tank body is failing and the unit is a replacement, not a repair: close the cold supply and the gas or power if safe, and call. Sediment that colours the water without corrosion can usually be flushed at the drain valve.