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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