Drinking water looks ordinary to most of us; yet whatever its source, its quality can change in the distribution system, in tanks and in plumbing. For this reason hotels, schools, hospitals, building management and food facilities must have regular analysis done. The basic legislation is the Regulation on Water Intended for Human Consumption.

Parameter groups

Microbiological: E. coli and Enterococcus must be absent in 100 ml; coliform bacteria and the 22 °C colony count show the cleanliness of the system
Chemical: Nitrate (50 mg/L), nitrite, ammonium, arsenic (10 µg/L), lead (10 µg/L), cadmium, chromium, nickel, fluoride, chloride (250 mg/L), sulphate, sodium
Indicator: pH (6.5–9.5), conductivity (2500 µS/cm), turbidity, colour, odour, taste, free chlorine

When should you have it analysed?

Routine: For mains-connected facilities microbiological every three months and a full analysis once a year; those using well or tanker water are advised monthly microbiological monitoring
After an event: Pipe repair, tank cleaning, water cut, flood or a change in colour or odour
New facility: Before opening and monthly for the first six months
Sensitive groups: More frequently, including Legionella, for hospitals, care homes and baby-care centres

How is a sample taken?

A sterile 500 ml bottle is used. The tap mouth is disinfected with alcohol or flame, the water is run for two to three minutes, the bottle is filled without touching its inside and closed tightly. For chlorinated mains water the bottle must contain sodium thiosulphate, which neutralises the chlorine and prevents the killing of microorganisms. A separate 2 L plastic bottle is used for chemical analysis and a separate acidified bottle for heavy metals. The sample must reach the laboratory at 2–8 °C and within 24 hours at the latest.

When a result exceeds the limit

First the possibility of a sampling error is assessed and verified with a new sample. If verified, the source is determined (tank, plumbing, source water), disinfection or filtration is applied and analysis is repeated until conformity is achieved. With our full drinking-water analysis package you can see 34 parameters compared with the regulation limits.

Common mistakes

Taking a sample without disinfecting the tap mouth, using a non-sterile bottle, touching the inside while filling and keeping the sample longer than a day spoil the microbiological result. Taking a sample only from the mains inlet instead of the tank outlet does not show the real state of the plumbing; sampling from different points and planning the points is recommended.

To whom do you submit the report?

Municipalities, health directorates, tourism licence inspections and insurers ask for an accredited laboratory report. We issue your report with a statement of conformity alongside the regulation limits so that no additional explanation is needed at inspection.

When and With Which Parameters Should Drinking Water Be Analysed?