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Facts: Sampling Water Properly

There is a large variety of different containers and bottles for sampling water and other substances available and the laboratories do have their distinct requirements along those lines. Amber Glass, Teflon Lined, No Head-Space, Clear Glass (Jar) and Plastic Bottle are just a few and they all serve a very specific purpose.

For the evaluation of water and respective treatment systems, based on the Canadian Drinking Water Quality Guidelines, a lab usually requires diferrent types of containers with diferrent preservatives, regularly resulting in numerous containers required.

A small Glass Jar (100 ml) for example, is used to sample water for the bacteria test; a small plastic bottle (100 ml) for the metal scan and third plastic bottle (usually 500 ml) for the chemical test sequence. Additional and more specific tests might even require yet different types and then again, each lab might have their distinct prerequisites on top.

Since the bacteria test is crucial (i.e. for real estate transactions it is a legal requirement), the bottle for this test needs to be sealed and a small amount of powder, a preservative, which significantly slows down the reproduction rate of bacteria, needs to be in the bottle. If any of these criteria is missing, do not use the bottle for that purpose!

Before sampling the water into the bottles, take a look at the source. If tap water is sampled, the outlet needs to be disinfected. In order to do it properly, it is strongly recommended to take off the sieves from the faucet and disinfect the edges and inside with for example some cleaning alcohol and a small swap.

Raw water sampling is best done, when – besides the same precautionary cleaning measures as described above – the water has run for a few minutes before the actual sample is taken.

In case other and stronger disinfectants have been used within the water supply, e.g. for well-shocking procedures (such as bleach or similar) it is necessary to make sure, no residual disinfectants are left, since this would compromise the results.

When filling the bottles, we recommend using disposable gloves, at least for the hand, which deals with the lids of the bottles (and of course nothing else should be touched during this time). It is very easy to introduce compromising influences and results from the lab are too important to take chances.

Always fill the bottles right to the very top (without flushing out any of the powder in the bacteria sample bottle) because that way the oxidation process is slowed down greatly. The less air in the bottle – the better! Some lab bottles show so called fill marks and that is fine. But if in any doubt, fill the bottles right to the top – the lab can remove the amount of water necessary afterwards.

For our purpose, a so called CoC- or Chain of Custody Report needs to be filled in and be provided to the lab. It clearly needs to identify the Regulatory Requirements, the tests to be performed and other important data.

The water temperature will be measured at the time the sample is dropped off at the lab. With the temperature between 1°C and 10°C the sample is considered in good order in that respect. Time is another parameter. If the sample has been taken more than 24 hours prior to drop off time, the sample is unusable for proper bacteria testing.

As you can see, it is certainly necessary to sample water with due diligence and it makes sense. What would be any lab report good for, if the basis for the analysis had been undermined prior to the testing?

Thank you for your interest

Your Perfet Water Nova Scotia Team