What it is
Odour is assessed by trained analysts and reported as a dilution number, in the same way as taste. Clean water has little or no smell.
Where it comes from
A rotten-egg smell is hydrogen sulphide from bacteria in boreholes, hot-water cylinders or stagnant tanks. Earthy or musty smells come from algae and organic matter in surface-influenced supplies. Chlorine smells come from disinfection. Petrol or solvent smells suggest contamination and need investigating urgently.
Why it matters
Odour is an aesthetic parameter with a guideline of acceptable and no abnormal change. Most odours are not harmful, but a sulphide smell can indicate bacterial activity and a chemical smell can indicate contamination, so an odour result is always read alongside the microbiological and chemical findings.
What can be done about it
Sulphide odours are treated with aeration, oxidation or chlorination followed by filtration, and by disinfecting the hot-water system if that is the source. Musty odours respond to activated carbon. Chemical odours call for finding and removing the source before any treatment.
Information last reviewed 5 October 2026 by Pozzani Pure Water.