Why Does My Water Smell Like Rotten Eggs?

Few plumbing problems are as off-putting as a rotten-egg smell coming from your taps. The odour, caused by hydrogen sulphide, most often points to a reaction inside your geyser or bacteria in the system.

Is it the hot water, the cold, or both?

This is the most useful first test. If the smell is only in the hot water, the geyser is the likely source. If it is in both hot and cold, the issue is more likely in the water supply or the incoming line. Run the taps and note where the smell appears; it narrows the diagnosis quickly.

Common causes

• The geyser anode rod. Geysers contain a sacrificial anode that protects the tank. In some water conditions it can react and produce the hydrogen sulphide smell, especially in hot water that has sat for a while.
• Bacteria in the tank. A geyser left at too low a temperature, or unused for a period, can develop odour-causing bacteria.
• Stagnant water. Water that has sat in pipes during an absence can develop a smell that clears after running the taps.

What to do about it

• If only the hot water smells, have a plumber inspect the geyser and the anode. Replacing or changing the anode type can resolve it.
• Flushing and properly heating the geyser can clear bacterial odours. A qualified plumber can do this safely as part of a service.
• If both hot and cold smell, and especially if neighbours have the same issue, contact your municipality. It may be a supply-side problem.

Frequently asked questions

Why does only my hot water smell of rotten eggs? That usually points to the geyser, often a reaction involving the sacrificial anode or odour-causing bacteria in the tank. A plumber can inspect and resolve it.

Is rotten-egg-smelling water dangerous? The smell is unpleasant and worth fixing, but is often a nuisance issue from the geyser rather than a health emergency. If both hot and cold water smell, check with your municipality.

Can I fix smelly geyser water myself? Some causes need a plumber to inspect and possibly replace the anode or flush the tank safely. Geyser work also has compliance implications, so professional help is wise.

Sources

• Michael's Plumbing, Common Plumbing Questions

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