Disinfect the water lines of the treatment unit

According to the KRINKO recommendation, water from the treatment unit should contain no more than 100 colony-forming units per millilitre and fewer than one Legionella per millilitre. Daily flushing is part of the routine. A rising germ count points to a biofilm in the thin tubing. biostream® ZERO uses chlorine dioxide to disinfect the complete treatment unit: handpieces, turbines and all water-carrying lines.

Proven: 99.9 % efficacy against germs occurring in drinking water, established in 1,620 individual tests by Leibniz University Hannover at a contact time of 5 minutes. The study in detail

Advice for your practice Information sheet for dentists (German)

Treatment unit in the dental practice is an application of biostream® ZERO in which the water lines of a dental unit are disinfected with chlorine dioxide.

Key facts

Product: biostream® ZERO
Guide values: KRINKO recommendation 2006: no more than 100 colony-forming units per millilitre, fewer than one Legionella per millilitre
Regulatory framework: KRINKO "Infection prevention in dentistry", Drinking Water Ordinance and the list under Section 20 TrinkwV
Standard: GEOhybrid grounding
Last updated: 23 September 2026

What requirements apply to the water in the treatment unit?

The water fed in must meet the requirements of the Drinking Water Ordinance. As guide values, the 2006 KRINKO recommendation names a colony count of 100 per millilitre and fewer than one Legionella per millilitre. If the water is used to treat severely immunosuppressed patients, it must be free from Pseudomonas, Cryptosporidium and Legionella.

The recommendation "Infection prevention in dentistry" from the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute has been listed among the earlier recommendations since 2021 and is no longer updated. As long as there is no newer body of knowledge on water from dental units, its statements can, according to the RKI, still serve as a reference. For subject-specific questions, the RKI refers to the German Dental Association and the specialist societies. According to its own description, this task is met by the hygiene guide of the German Working Group for Hygiene in Dentistry (DAHZ), whose 17th edition is dated 31 March 2026.

Requirement	Value or rule	Source
Water fed in	must meet the requirements of the Drinking Water Ordinance	KRINKO 2006
Colony count	guide value 100 per ml; under DAHZ, 100 CFU/ml at 36 °C counts as the warning value	KRINKO 2006; DAHZ 2026
Legionella	guide value below 1 CFU per ml	KRINKO 2006
Severely immunosuppressed patients	water free from Pseudomonas, Cryptosporidium and Legionella	KRINKO 2006
Materials	should have passed testing under DVGW W 270	KRINKO 2006
Connection to the drinking water installation	physical separation under DIN EN 1717, for example a free outlet of type AA, AB or AD	DAHZ 2026; LZK Baden-Württemberg

How do you keep the water lines of the treatment unit clean?

With daily flushing, regular water testing and, if the colony count rises, disinfection agreed with the manufacturer of the unit.

The steps in detail

Flush in the morning. At the start of the working day, flush all water-carrying systems without transmission instruments attached, at all outlets, including the cup filler, for 2 minutes.
Flush after every patient. Flush the cooling water outlets used for at least 20 seconds with water, and additionally with air if necessary.
Flush at the end of the treatment day. After the last patient, flush the water-carrying systems in the same way.
Have the water tested regularly. Trained staff take the sample after the water has been running for 20 seconds. Where there is no indication of any deficiency, the KRINKO considers intervals of 12 months reasonable.
Investigate unusual readings. If the colony count is above the warning value of 100 CFU per ml, flush intensively and have the test repeated.
Fight the biofilm. According to the KRINKO, higher colony counts point to extensive biofilm colonisation. In that case, more intensive flushing before treatment and, if necessary, disinfection agreed with the manufacturer of the unit are required, for example with biostream® ZERO via the built-in disinfection unit or a bottle-care system.

Sources: KRINKO 2006, item 5; DAHZ hygiene guide 2026, chapter 10.

The complete treatment unit in view

Whether the practice uses a built-in disinfection unit or a so-called bottle-care system, hygienically flawless drinking water should be present in the treatment unit at all times. biostream® ZERO disinfects the complete treatment unit and the handpieces, turbines and all water-carrying lines connected to it. Biofilm that has already formed is fought as well.

Material compatibility plays a particular role for equipment of high material value. In our experience, the optimised pH value of biostream® ZERO makes corrosion almost impossible. Fungi, algae, viruses and pathogenic germs, known technically as Pseudomonas, E. coli and Legionella, are killed by the active substance chlorine dioxide.

biostream® ZERO has been used against biofilms in dental practices for years.

Dental instruments with the water lines of the treatment unit

Why chlorine dioxide instead of hydrogen peroxide?

Most of the disinfectants available on the market for dental units are based on hydrogen peroxide. In the list of permitted treatment substances under Section 20 of the Drinking Water Ordinance, hydrogen peroxide is listed for oxidation only, whereas chlorine dioxide is listed for disinfection. Under DVGW code of practice W 291, hydrogen peroxide must be dosed 25 times as strongly to achieve the same effect as the active substance chlorine dioxide.

After treatment, drinking water may contain no more than 0.1 mg/l of hydrogen peroxide. After disinfection with hydrogen peroxide it must therefore be flushed out almost completely, and every extra rinsing step costs money. The page methods compared shows the comparison of all methods.

biostream® ZERO in figures

Scientifically proven, independently tested and field-proven in dental practice.

Proven efficacy

99.9 %

In 1,620 individual tests by Leibniz University Hannover against germs typically found in drinking water, at a contact time of just 5 minutes.

Ready to use in

3 hrs.

From preparation to a ready, highly effective disinfection solution, without complex plant technology.

Dosage required compared with hydrogen peroxide

25×

lower: 6 instead of 150 mg/l for disinfecting installations, under DVGW code of practice W 291. Evidence

Efficacy tested. In 1,620 individual tests at the Institute of Food Science and Human Nutrition of Leibniz University Hannover (led by Dr. rer. nat. H.-D. Werlein), biostream® ZERO was shown to have an efficacy of 99.9 % against germs occurring in drinking water, at a contact time of 5 minutes.

Study, methodology and scope in detail ›

Your advantages

Ready to use within just 3 hours
For built-in disinfection units and bottle-care systems
Effective across the entire drinking water pH range
25 times lower dosage requirement than hydrogen peroxide (6 instead of 150 mg/l for disinfecting installations, DVGW code of practice W 291)
Highly effective against Pseudomonas aeruginosa, Escherichia coli & coliform bacteria, as well as Legionella (Legionella pneumophila)
Free from heavy metals (silver, copper)
Oxidative action on the cell membrane, proteins and genetic material at the same time, not at a single point of attack

Rules and standards for chlorine dioxide

Drinking Water Ordinance (TrinkwV), Section 20: chlorine dioxide is included in the list of permitted treatment substances for disinfection
DIN EN 12671: chlorine dioxide generated on site for the treatment of drinking water
DVGW W 224: methods for the disinfection of drinking water with chlorine dioxide
DVGW W 291 and W 551-3: chlorine dioxide as a proven chemical for cleaning and disinfecting installations
Guideline No. 5 of the working group of the German coastal states on ship hygiene: chlorine dioxide for drinking water on board
DIN 2001-2: drinking water supply from non-stationary installations such as motorhomes and boats

What each rule means ›

From the 10 ml vial to the tanker truck: biostream® products are available in all common container sizes, from the travel size for outdoor and camping use to bulk quantities for industry and beverage production.

biostream® ZERO asepticaPRO

May a disinfection system be connected to the practice's drinking water installation?

Only downstream of a system separation. The DAHZ hygiene guide 2026 points out that DIN EN 1717 requires a physical separation between the drinking water installation and the treatment unit. The guide considers installing a disinfection system within the drinking water installation itself permissible under Section 23 of the Drinking Water Ordinance only if the health authority has ordered it. Section 23(3) governs the case where the condition of the installation is the cause of microbiological deficiencies: in that case, disinfection there may only be carried out on the order of the health authority, and the operator must remediate the installation. According to the guide, a disinfection system downstream of a system separation that supplies only the dental units, and is therefore not part of the drinking water installation, is permissible.

The guide also points out that a free outlet within the treatment unit is a weak point from a hygiene perspective.

In its guide, the Baden-Württemberg regional dental association names, for treatment units supplied via the drinking water line, protective devices from the "free outlet" group for fluid category 5: types AA, AB and AD.

Who monitors water hygiene in the practice?

Under Section 23(6) of the Infection Protection Act, the health authority may carry out infection-hygiene monitoring of dental practices. In Baden-Württemberg, according to the regional dental association's guide, the regional councils (Regierungspräsidien) also check, as part of monitoring the reprocessing of medical devices, whether treatment units are equipped with a protective device under DIN EN 1717.

As early as May 2015, the Thuringia regional dental association published an information sheet titled "Hygiene inspections and checks under medical device law in dental practices" (in German). It also covers the water-carrying systems of treatment units. In its factsheet "Information on water-carrying systems in the dental treatment unit" (in German), the Baden-Württemberg State Health Office (LGA BW) addresses microbial contamination and biofilm formation.

Based on its own experience, the LGA BW recommends taking water samples roughly every three to six months, depending on the previous result, and having them tested not only for colony-forming germs but also for Pseudomonas aeruginosa, since this germ is held responsible for biofilm formation. The LGA BW also states: "Tests for Legionella need not be carried out more than once a year if the previous result showed no corresponding detection of the germ."

Frequently asked questions about water hygiene in the dental practice

How long must the treatment unit be flushed in the morning?

According to the KRINKO recommendation and the DAHZ hygiene guide, for 2 minutes at the start of the working day, at all outlets including the cup filler, without transmission instruments attached.

How often must the water in the treatment unit be tested?

Where there is no indication of any deficiency, the KRINKO considers intervals of 12 months reasonable. If the colony count is above the warning value of 100 CFU per ml, the DAHZ hygiene guide provides for intensive flushing and repeating the test.

What must be done if the colony count is above 100 CFU per ml?

If this warning value is exceeded, the DAHZ hygiene guide provides for identifying the cause: flush intensively and repeat the test. According to the KRINKO, higher colony counts point to extensive biofilm colonisation. In that case, more intensive flushing before treatment and, if necessary, disinfection agreed with the manufacturer are required.

Is biostream® ZERO suitable for bottle-care systems?

Yes. biostream® ZERO can be used both via built-in disinfection units and via bottle-care systems. Follow the specifications of your treatment unit's manufacturer.

Does chlorine dioxide attack instruments and lines?

In our experience, the optimised pH value of biostream® ZERO makes corrosion almost impossible. If in doubt, clarify material compatibility with your unit's manufacturer.

Why is flushing alone not enough?

Biofilms form on surfaces in contact with water and protect the germs from being flushed out. Flushing lowers the germ count in standing water, but it does not remove the biofilm on the tubing wall. According to the KRINKO, higher colony counts point to extensive biofilm colonisation; disinfection may then become necessary. More on this under fighting biofilms.

Information sheet for dental practices

This PDF information sheet explains how to disinfect treatment units with biostream® ZERO concentrate, removing biofilms and bacteria.

Download the information sheet for dentists (German)

Further reading. We provide basic knowledge and information sheets in one place. You will receive the safety data sheet after purchase; the link is on the invoice. To the information sheets ›

What it is not

Treatment unit in the dental practice is an application and not a separate product: biostream® ZERO is used; quantities and contact times are given in the dosing instructions, not on this page.