How to Properly Collect Water Samples for Testing

Proper water sampling is a key stage in the entire testing process. Even the best-equipped laboratory won’t be able to deliver reliable results if the sample was collected incorrectly. That’s why today we’re sharing how to do it right—both for microbiological and physicochemical testing.

What type of bottles should you use?

• Microbiological testing - only in sterile containers, which we provide FREE OF CHARGE at our laboratory.
• Physicochemical testing - you can use a regular plastic bottle from still mineral water.

If you're collecting samples for both types of testing from the same location, always start with the physicochemical sample. Only afterward should you disinfect the tap and collect the microbiological sample.

Step-by-Step: Collecting Water Samples for Microbiological Testing

1. Preparing the tap
   • Check for leaks and remove filters, screens, or extensions.
   • Wash the spout with soap and water, rinse thoroughly.
   • Disinfect a metal tap with 70% alcohol and flame it.
   • For plastic taps, soak the tip in alcohol for about 10 minutes (do not flame!).
2. Flushing the tap
   • Turn the water on for 5–10 seconds, then reduce the flow.
   • Usually, 2–3 minutes of flushing is enough, but if the water has been standing in the pipes, it may take up to 30 minutes.
3. Collecting the sample
   • Open the sterile bottle just before sampling—do not touch the inside of the cap.
   • Fill the bottle to the marked line (500 ml) without turning off the tap while filling.
   • Important: Do not dip the bottle in a bucket or touch the tap with it.
4. Other water sources
   • Well with a pump – a short flush is enough, no need to disinfect.
   • Well without a pump – discard the first three buckets of water, then collect the sample.
   • Rubber hoses – cut off the tip, disinfect with alcohol, flush for 10 minutes, then take the sample.

Step-by-Step: Collecting Water Samples for Physicochemical Testing

1. Preparing the site
   • Check the tap for leaks and remove any filters, screens, or extensions.
   • Rinse the tap outlet with water.
2. Flushing the tap
   • Open the tap for 5–10 seconds, then reduce the flow.
3. Collecting the sample
   • Open the bottle right before sampling, without touching the inside of the cap.
   • Fill the bottle so that the water flows freely and flushes the bottle at least twice its volume.
   • Fill the bottle completely—there should be no air bubbles under the cap. Close it immediately.
4. Transporting the Sample
   • Label the sample.
   • Deliver it to the laboratory as soon as possible.
   • Avoid overheating or excessive cooling of the sample.

Attach a completed form - available on our website under the tab:

Drinking Water – Mikrolab Microbiological Laboratory

Sample Drop-off Hours

• Microbiological testing – Monday to Friday, 08:00–14:30
• Physicochemical testing – Monday to Thursday, 08:00–13:00

Why Is This So Important?

An improperly collected sample can:

• lead to distorted results,
• require repeat testing (which means lost time and money),
• prevent a proper assessment of your water’s actual quality.

That’s why it’s always worth following the lab’s instructions – it ensures reliable results and gives you a clear picture of your water’s quality.

If you have any doubts – get in touch with us. Our team will be happy to guide you through the entire process.