What types of water
are there?

According to legal requirements, water for human consumption can be roughly divided into:

  • Service water (e.g. gray water)
  • Swimming and bathing pool water
  • Drinking water (e.g. mineral water)

Service water is used in cooling systems. If the water is taken from a private well and used exclusively for garden purposes – i.e. it is not fed into the household plumbing system – it is also referred to as process water.

Each of these waters has its own legal requirements for quality and purity. Even if these waters are not intended for drinking, they must comply with minimum legal requirements regarding their quality. This water testing must be carried out by an approved laboratory.

Is tap water safe to drink?

Tap water is a commonly used term for “water found in pipes.” Not all water from a pipe is suitable for drinking. Water for watering the garden, of course, does not have to meet the same standards as drinking water for baby food.

Drinking water is water that is “intended for human consumption,” i.e., when it is used for drinking, cooking, and preparing food as well as beverages. This also includes the use of drinking water for personal hygiene such as showering, as well as cleaning objects that come into contact with the body or food.

Water is also considered drinking water if it is used in a food processing plant in the manufacture of products. According to the law, this must be safe, edible and free of pathogens. That is, tap water is safe to drink because it is intended for human consumption and therefore must be safe for humans.

However, the quality of tap water is only guaranteed by the public utility company up to the house connection. However, the connecting piping system can have a great influence on the quality of the drinking water, for example, old lead pipes or other unacceptable materials that negatively affect the drinking water.

It makes sense to check the tap water at the point of consumption by means of water testing if it is to be used as drinking water.

Is well water safe to drink?

Well water comes from a well that is fed by groundwater, which is then transported to the top with the help of a pump. Well water is therefore drinking water if it is for human consumption and, in accordance with legal requirements, must be tested for its microbiological and chemical-physical quality by regular water testing by an accredited laboratory. Water from wells often flows through different layers of rock and can therefore contain dissolved substances and also bacteria that are harmful to health.

These bacteria can settle and multiply in the domestic installation.

Anyone who uses well water as drinking water has an obligation to notify the relevant health authority.

The laboratories of the Tentamus Group offer water testing for all these industries – process water, cooling tower water, swimming pool water, mineral water and drinking water.

We are also happy to support you with our professional expertise in the classification of your water.

Water analysis water quality

What can affect
the quality of water?

The quality of water can be affected by many factors and is of great importance to be able to ensure safety and health. Especially germs and pollutants, such as heavy metals, are responsible for quality degradation and can be detected in time by regular water testing.

The microorganisms to be tested according to the Drinking Water Ordinance include:

  • Colony count at 22°C and 36°C
  • E. coli
  • Coliform bacteria
  • Enterococci
  • Legionella
  • Clostridium perfringens
  • Pseudomonas aeruginosa

These can be hazardous to health through consumption or inhalation and can cause serious infections.

Pollutants that affect quality and therefore health include:

  • Sediment, turbidity
  • Nitrate, nitrite
  • Ammonium
  • Heavy metals
  • Pesticides
  • Hydrocarbons

Furthermore, the quality is determined by the mineral composition of the water:

  • Hydrogen carbonate
  • Calcium
  • Magnesium
  • Potassium
  • Iron
  • Sodium
  • Sulfate
  • Chloride
  • Calcite/calcium carbonate ( scale)

Advantage of water testing in the laboratory
over test kits

Various quick tests can be purchased in stores, so that water can be tested itself using test strips. However, these are only of limited value because the water sample is not taken by a trained sampler. This can quickly lead to impurities or contamination and the measured values can be falsified.

To obtain meaningful test results, a number of measures are mandatory in water testing:

  1. Control of the precision of the measured value – Suitable/calibrated equipment and validation of the procedure
  2. Control of the measured value reference – Important is the sampling in the “right” part of the plant
  3. Control of the measured value risk – Interference factors must be excluded/considered (this applies in particular to the use of kits and for microbiological samples)
  4. Control of the accuracy of the measured values – Precise measurement results through special test procedures
  5. Control of the interpretation of the measured values – Which influencing factors have to be considered?
  6. Control of the measured value evaluation – Is the measured value valid?
  7. Control of the effect of the measured value – Is there a temporary increase/a systemic problem?
  8. Appropriate reaction – Which measures have to be taken/ what are the consequences?
For drinking water analyses, such a test is not accepted by the health authority, since the measured values obtained are not reliable with regard to the points mentioned above. Mandatory testing of drinking water may therefore only be performed by accredited laboratories with samplers explicitly trained for water testing.

In addition, only an undefined snapshot is obtained with test kits. The results obtained cannot be assigned to an origin. This means that no concrete measures can be derived either.

Through good planning of sampling with regard to relevant taps and the type of water samples, reliable and coherent results are obtained through water testing. Based on these results, action plans can be drawn up and possible sources of contamination can be detected in order to ensure the quality of the water or to prevent quality losses and possibly damage to the installation.

Limit Values Water

Relevant limit values for drinking water analysis

The requirements for drinking water analysis are regulated in the Drinking Water Ordinance (TrinkwV). The laboratories of the Tentamus Group are approved, among other things, for the sampling and analysis of drinking water. The annex to the Drinking Water Ordinance lists limit values for the microbiological and chemical parameters that are tested in our water testing.

Limit values for chemical parameters

Annex 2 of the Drinking Water Ordinance lists limit values for chemical parameters in drinking water. Depending on the pipes, various heavy metals are relevant, e.g. lead values are more important in old buildings than in new buildings, as old lead pipes are sometimes still installed here.

Chemical substances must not be present in concentrations that would harm humans. This can be detected with the help of chemical water testing.

In the following, we list essential limit values for heavy metals. The entire table can be found in the Ordinance.

Parameter Grenzwert mg/l
Arsenic 0,01
Lead 0,01
Manganese 0,05
Copper 2,0
Nickel 0,02

Microbiological testing
of drinking water

Drinking water naturally contains microorganisms. However, it must be ensured that the concentrations here are harmless to humans. According to the Infection Protection Act, microorganisms must not be present in drinking water in concentrations that are hazardous to health. Due to technical errors in the construction of the drinking water supply system or insufficient water treatment, limit values can quickly be exceeded and endanger people. To prevent this, the Drinking Water Ordinance lays down strict requirements for both monitoring and compliance with drinking water quality.

Landlords, owners and operators must ensure that drinking water is regularly tested by means of reliable water testing.

The microbiological scope of testing includes:

  • Determination of the colony count at 22°C and 36°C – The total colony count in the water is determined by exposing the water sample to incubation temperatures of 22°C and 36°C. The results do not provide information about the presence of a specific germ, but about the general microbiological status of the sample. The results do not provide information about the presence of a specific germ, but about the general microbiological status of the sample.
  • Coliforms – Coliform germs comprise a whole family of germs. Among them are also pathogenic germs – i.e. bacteria that can make people ill.
  • E. coli – Escherichia coli (E. coli) belongs to the coliform bacteria and is found in the intestine. It is an indicator germ. If E.coli is found in a water sample, it is an indicator of poor hygiene and indicates faecal contamination.
  • Enterococci – Enterococci are intestinal bacteria of humans. The presence of enterococci in water is also an indicator of faecal contamination.
  • Clostridium perfringens – Clostridium perfringens are gram-positive, anaerobic bacteria. They belong to the intestinal flora of humans and animals. Drinking water is tested for Clostridium perfringens if the water comes from surface water or is influenced by it. This also means mandatory testing for wells that are less than 10 m deep.
  • Pseudomonas aeruginosa – Pseudomonas aeruginos belongs to the gram-negative bacteria and can occur wherever there is sufficient water. This germ is particularly resistant and belongs to the slime-forming bacteria.
  • Legionella – Legionella are gram-negative, aerobic bacteria that are transmitted via droplets. This means that an infection is caused, for example, by inhaling water vapour containing legionella. They are mainly found in hot water pipes. According to the Drinking Water Ordinance, the technical action value is 100 CFU/100 ml.

Water testing to
check the water quality

Stagnation test

If water stagnates, i.e. stands in the pipe for a longer period of time, for example after a holiday or a company closure, substances contained in the pipes can pass into the water and thus significantly change the quality of the tap water.

In a stagnation test, the parameters pH value, conductivity and temperature, as well as relevant heavy metals, are measured and examined.

Testing water hardness

The total hardness of water is based on the concentration of magnesium and calcium ions, calculated as carbonate hardness. Hard water contains more magnesium and calcium ions than soft water. In Germany, water hardness is expressed in “German degrees of hardness” (dH°) and according to European law in millimoles of calcium carbonate / litre. In the Drinking Water Ordinance (TrinkwV) there are no limit values for hardness, there is only a classification into the 3 following hardnesses:

Total hardness (dH°) Millimol Calcium Carbonate / l Range
< 8,4 < 1,5 soft
9,4 - 14 1,5 – 2,5 medium hard
> 14 > 2,5 hard

Water suppliers are obliged to publish the total water hardness once a year unless it changes. If the water hardness changes, it must be published immediately.

of laboratories
of the Tentamus Group

All Tentamus Group laboratories that carry out water testing, including sampling, are approved in accordance with the Drinking Water Ordinance and accredited to ISO 17025. With us, you get everything from a single source:

  1. Expert knowledge and advice
  2. Requirement profiles for water
  3. Sampling planning
  4. Sampling
  5. Water testing
  6. Accompanying recommendations for measures
Sampling Water analysis

How does sampling for water testing work?

According to the Drinking Water Ordinance, sampling for water testing of drinking water may only be carried out by accredited laboratories. Accordingly, this also applies to well water used as drinking water and to cooling tower and process water and swimming and bathing pool water. Here, however, there are other requirements for taking water samples.

In water testing, the sampling of drinking water depends on the purpose of the analysis:

Thus, there are different purposes for sampling. Each purpose has its own requirements for water sampling and provides specific results. If these requirements are disregarded, the results will be of limited or no significance.

For example, when sampling from the water supplier for a microbiological examination, the water sample is taken at the transition from the water supplier to the house. If a treatment plant is installed, sampling must also be well timed in many cases. Otherwise, only limited or no meaningful results are obtained.

Under certain circumstances, limit values may be exceeded, which can be avoided with good planning in advance. Because there are so many possibilities for contamination, good planning and execution of sampling is mandatory for meaningful water testing.

Staff who conduct sampling for drinking water analysis receive regular and extensive training to ensure proper sampling of water samples.

How are the results of water testing provided?

The results of the laboratory analyses are assessed by our experts and you receive a clear and comprehensible test report with the test results of the water testing. Transmission of the results to the competent health authority can also be arranged. The duration of the analysis depends on the parameters and can vary between 4 and 10 days. A water test for legionella, for example, takes an average of 10 to 12 days.

Who should have their water analysed in a laboratory?

  • Entrepreneurs and owners of water supply systems are obliged to carry out water testing.
  • Private households can have the general quality of their water tested with the help of water testing or do so on suspicion, e.g. if they suspect legionella or heavy metals.
  • Service providers where customers come into contact with water, such as dentists, should also have their water tested regularly, as hygiene and safety are of particular importance here.
  • Landlords of apartment buildings are responsible for the water quality and are obliged to have it checked. Here, the public health department decides which parameters must be tested for in addition to legionella. One- and two-family houses are exempt from this obligation.
  • Commercial and industrial facilities with a central water heating system are also obliged to have the water checked regularly if they have a storage water heater or a flow-through water heater with a total capacity of more than 400 litres or if a volume of 3 litres is exceeded from the outlet of the water heater to the first tapping point.
  • Large public systems are obliged to carry out a legionella examination once a year and large commercial systems every 3 years.

If the technical measure value for legionella is exceeded, the result must be sent to the public health department, as there is a reporting obligation directly for laboratories. If another limit value is exceeded, e.g. for heavy metals or other parameters, these test results must also be reported to the public health department. Furthermore, the operator is obliged to report anything that could have an influence on the drinking water, e.g. modification of the filter system/pipe network, incidents within the protection zone, change of ownership, etc.

Overview of laboratories for water testing of the Tentamus Group

The following laboratories from the Tentamus Group offer water testing:

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