How to Prepare a Water Sample for Microbiological Testing

A microbiological result can only ever be as good as the sample behind it. Water is especially unforgiving: microorganisms continue to grow or die after collection, so the way you sample, store and transport water decides whether the laboratory result reflects reality.

Start before you collect

Contact the laboratory before sampling. Container type, sterility, minimum volume, temperature and maximum holding time all depend on the method — and requirements confirmed in advance prevent wasted trips.

As a rule, microbiological water samples require sterile containers, careful aseptic technique, protection from heat and prompt delivery. Do not touch the inside of the container or cap, and do not rinse a sterile container before use.

At the sampling point

• Label the container before filling, with the sampling point, date and time.
• Flush taps where appropriate, following the agreed procedure.
• Fill to the indicated level — some methods need headspace; do not guess.
• Close the container immediately and keep it upright and protected.

Transport and delivery

Keep samples cool and out of direct sunlight, and deliver them within the holding time confirmed at booking. Record the collection date and time accurately — the laboratory uses it to judge whether the sample remains valid.

If the water contains disinfectant residual, or you suspect contamination or any hazard, tell the laboratory when booking. The more the laboratory knows, the more meaningful the result.