Bosch Bacterial Contamination / Anode Reaction (Storage-Type Bosch Heaters)

Bosch water heater's hot water output smells like rotten eggs (sulfur odor)

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Reaction between sacrificial anode rod and sulfur in water, Bacterial growth in warm stagnant water, Low hot water usage patterns

How to Fix / Troubleshooting

Safety first: Turn OFF power or gas and allow the water heater to cool before draining or servicing. Hot water can cause severe burns.

  • Flush tank (storage models): Drain several gallons from the tank through the drain valve to remove sediment. Refill and repeat if odor persists.
  • Disinfect system: A plumber can chlorinate the tank and plumbing to kill odor-causing bacteria.
  • Anode rod options: Consider replacing the magnesium anode rod with an aluminum/zinc alloy rod designed to reduce odor. This should be done by a professional familiar with Bosch storage heaters.
  • Increase usage / temperature: Periodically raising the water temperature (within safe limits and with scald protection) and using more hot water can reduce stagnation.
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Repair Difficulty

Medium 3/5

Required Part

Anode Rod
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