A noisy geyser is usually trying to tell you something. Most sounds have a specific cause and most causes are fixable before the geyser fails completely.
Rumbling or popping
A low rumbling or popping sound during heating is almost always scale buildup on the element. Bloemfontein's water is relatively hard, and calcium carbonate deposits on the element surface cause hot spots that pop as the element heats. Heavy scaling reduces efficiency and eventually burns out the element. A descaling treatment or element replacement fixes it.
High-pitched whining or whistling
A constant whine or whistle, especially under pressure, often points to the pressure control valve or vacuum breaker malfunctioning. It can also be a sign of the geyser overheating because the thermostat has failed. If the overflow pipe outside is also running, the thermostat is allowing the water temperature to rise too high - this is a safety issue that needs immediate attention.
Banging or knocking
A single bang followed by silence might be water hammer in the supply pipes. Repeated banging from inside the geyser tank is more concerning - it can indicate a tank that has developed an internal defect and may be close to failure. Have it assessed before it fails completely.
Hissing from the overflow pipe area
A continuous hissing from the overflow pipe or the pressure control valve area is water leaking past a valve seat. The PCV may be stuck open or have a worn seat. Left unattended, this wastes hot water continuously and raises your electricity bill. It's a straightforward valve replacement.
Frequently Asked Questions
My geyser makes a loud pop every morning. Is that normal?
Very light expansion sounds as the tank heats are normal. Loud pops that you can hear from another room are scale buildup on the element and worth addressing.
At what point does a noisy geyser need to be replaced?
If the tank itself is leaking, replacement is the only option. Noisy elements, thermostats and valves are all replaceable components if the geyser is less than 8–10 years old.