Rotten-Egg Smell: A 30-Second Triage
Three different problems cause that sulphur smell, and each has a different fix. One glass of water tells you which one you’ve got.
By Danny Lachhman · Owner, 360WATER Systems Inc. · Orangeville, Ontario
Rotten-egg smell — hydrogen sulphide — is one of the most misdiagnosed problems in water treatment, because three completely different causes produce the same smell. Guessing wrong means buying equipment that was never going to fix it.
Start With the Glass Test
Fill a glass at the tap that smells worst. Walk away from the sink with it and smell it there. If the water in the glass smells fine, your water is not the problem — the smell is coming from the drain or the trap (biofilm in drains reeks of sulphur and fools everybody). That fix is cleaning, not equipment.
If the water itself does smell, run hot and cold separately:
- Hot water only: it’s your water heater. The magnesium anode rod in the tank reacts with naturally occurring bacteria and generates the gas right inside the heater. Fixes are anode-related — a different rod material or a powered anode — plus disinfecting the tank. No filter on earth fixes a smell that’s being manufactured in your heater.
- Hot and cold, at every tap: the sulphur is in the source water itself, which is common in wells around here. That one is treated at the source — oxidizing filtration or aeration treatment sized to your water — after a proper test tells us how much is there.
- One tap only, hot and cold: probably local to that fixture or its supply line — a rarely used bathroom is the classic case, and flushing it well is the first move.
Thirty seconds with a glass of water narrows it down before a single dollar gets spent. That’s how every water problem should start: figure out what it actually is, then fix that.
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