A water sample can be analysed for the microbiological and chemical parameters included in the chosen test package. Results apply to the tested parameters and that sample; they do not establish that the water is free of every possible contaminant. A suitable laboratory can provide a more comprehensive assessment of drinking-water quality.
What contaminants can be found in the water sample?
Both biological and chemical impurities can be found in the water sample, which can give an indication of the quality of the water and its suitability for drinking water. The most common findings are coliform bacteria, Escherichia coli, nitrates, heavy metals such as lead and arsenic, and various chemical compounds.
Biological contaminants
Microbiological impurities are often the most significant concern, especially in the case of well water. The presence of coliform bacteria and E. coli may indicate a problem with the hygienic quality of the water. The significance of the result and further actions will be assessed based on the test result, the structures of the well and the local environment.
Chemical contaminants
Nitrates can enter water from sources including agricultural fertilisers and can be harmful, particularly to infants. Other parameters of interest include lead, arsenic, manganese and iron. Testing may also measure pH, hardness, fluoride and selected organic compounds. The appropriate analyses depend on the water source and suspected problem.
How do you take a water sample correctly?
The container, sampling point, tap preparation, flushing time, transport temperature and delivery deadline depend on the analyses requested. Obtain containers from the laboratory and follow its specific sampling and transport instructions. Microbiological and chemical analyses may require different containers and handling.
What is the difference between microbiological and chemical water analysis?
Microbiological water analysis examines organisms present in water, such as bacteria and other microorganisms, while chemical analysis examines the chemical composition of the water, such as heavy metal concentrations, nitrates, and pH. The two types of analysis complement each other, and comprehensive water sample analysis often includes both.
Microbiological analysis is the primary tool when bacterial contamination is suspected or when the water originates from a well into which surface waters can enter. It tells us whether the examined sample meets the requirements or recommendations of the examined microbiological parameters. The result does not cover variables that have not been studied. Chemical analysis, on the other hand, indicates whether there are harmful substances in the water that are not visible in the microbiological examination at all, such as lead from old pipes or arsenic from the soil.
In practice, many water sample packages include both analyses, which gives the most comprehensive picture of the water quality. The microbiological result alone does not tell us anything about chemical impurities, and the chemical analysis does not detect bacteria.
When should a water sample be taken?
Test water when there is concern about its quality, and monitor a private well regularly. Well-water quality can change with the seasons, weather and local conditions.
Consider sampling when:
- the water has an unusual smell, taste or appearance
- there has been flooding or construction work near the well
- a household includes infants, a pregnant person or someone with weakened immunity
- the well has been unused for a long time
- there has been a nearby environmental accident or suspected contamination
- the well has not been tested for several years
For private wells in Finland, the Finnish Environment Institute’s Vesi.fi guidance recommends a basic analysis every three years and a broader analysis every six years. Test sooner if the water or well conditions change. Local guidance may differ elsewhere.
How long does it take to analyze a water sample?
The response time of the water sample depends on the laboratory and the assays ordered. Check the estimated completion time with the laboratory performing the study.
Once the results have been received, it is important to examine them in relation to the quality requirements for household water. If there are any deviations in the results, it is advisable to verify the result with a repeat sample, if necessary, and contact the health care or environmental authorities to investigate further measures.
Do you want to make preliminary measurements at home? Check out Testerit.fi’s water tests. Choose a test only according to the parameters stated in its user manual and, if necessary, verify the quality of household water with a laboratory test.
