Electric water heaters have one or two heating elements. When they fail, you get no hot water or insufficient hot water. This requires professional diagnosis and replacement.

If the pilot light won't stay lit, the thermocouple (safety device) has likely failed. This is a common issue with gas water heaters and requires professional replacement.

Rumbling/popping noises and reduced hot water indicate sediment (minerals) has built up at the bottom of the tank. This reduces efficiency and can damage the tank over time.

The Temperature & Pressure (T&P) relief valve is leaking or activating. This is a critical safety device that prevents tank explosions. It needs professional inspection and likely replacement.

Tankless water heaters require annual descaling and maintenance, especially in areas with hard water. Mineral buildup reduces performance and can cause complete failure.

Rusty hot water indicates corrosion inside the tank. The anode rod (which protects the tank) may be depleted, or the tank itself is corroding.

If hot water runs out quickly despite the heater being in good condition, you may have too small a unit for your household needs.

Fluctuating water temperature indicates a faulty thermostat that needs professional replacement.

Hissing sounds or pressure relief valve activation indicates high water pressure in your system, which can damage the water heater and plumbing.

Banging noises when water turns on/off indicate water hammer - a pressure surge that can damage pipes and water heater.

The dip tube directs cold water to the bottom of the tank. When it fails, cold water mixes with hot at the top, giving you lukewarm water.

The thermocouple is a safety device that shuts off gas if the pilot light goes out. When it fails, the pilot won't stay lit.

Tankless water heaters display error codes when they detect problems. These require professional diagnosis.

If the breaker is on and reset button has been pressed but still no hot water, there may be a wiring issue or failed component requiring professional diagnosis.

Persistent rusty water despite flushing indicates the tank interior is corroding. This cannot be repaired and replacement will be needed soon.