1. Water pooling beneath the unit
The most decisive sign. Once the tank itself has corroded through, there is no repair. Isolate the water supply and arrange replacement before the leak worsens.
2. Rusty or discoloured hot water
If discolouration appears only on the hot side, the tank interior or the anode is the likely source. Cold water discolouration points to something else in the supply.
3. Less hot water than there used to be
Sediment accumulating in the base of a storage tank reduces its effective capacity and insulates the heating source from the water. The tank is the same size; the usable volume is not.
4. Rumbling or banging while heating
Usually sediment. Water trapped beneath the sediment layer boils and moves, producing the noise. It indicates a tank that has been in service a long time.
5. Repeated repairs
Two or three service calls in a couple of years generally means money is being spent to delay an outcome rather than to prevent it.
6. Visible corrosion on the casing or fittings
Surface rust on the outer jacket, particularly around the base or the connections, is worth investigating. In coastal suburbs, external corrosion progresses faster.
7. Age beyond the expected service life
Many storage systems reach somewhere around eight to twelve years, though this varies by product, water conditions and maintenance. Continuous flow units often last longer. Check the data plate for the manufacture date.
Planning a replacement before failure is almost always cheaper and less disruptive than arranging one on the day the system stops.