Legionella control

Water treatment / Legionella control
legionella control

Experienced advisor in Legionella

Guldager, together with the Danish Serum Institute and the Danish Technological Institute, has led an EU project that mapped European countries' methods for legionella prevention in hot water systems. Guldager's Healthy Water concept is based on knowledge and common sense.

Legionella - a serious threat

Legionella is a bacterium that can be found anywhere there is water. It multiplies rapidly in places where the water is still and at a comfortable temperature of 30-40 degrees - which happens to be the same temperature we humans like to bathe in.

Unfortunately, Legionella is a dangerous bacterium that can cause respiratory infections in humans, sometimes with serious consequences. Legionella is spread in the air in small droplets, aerosols, such as when we turn on the shower, and can cause lung disease, which in some cases can be fatal.

Legionella help

Legionella is a problem everywhere we use hot water.

We have put all our efforts into finding practical solutions to the problem. We advise, analyse and find the right solution to avoid bacteria.

Contact a consultant

Call us +45 48 13 44 00 and find out how we can help.

Diana Torkelund
Diana Torkelund

Sales Engineer, Legionella Control

Erik Clausen
Erik Clausen

Area Sales Manager Funen & Jutland

Products for legionella control

Hyprolyser iSEC

Electrolysis-based disinfection system for continuous prevention of Legionella in hot water installations - using only salt, water and electricity.


Dynamic flow control valve for domestic hot water specially designed for flow control.

7 good rules to remember


Minimum 50°C throughout the circulating hot water system.
Also keep an eye on the temperature at the furthest tapping points in the building. During peak periods, it is to be expected that the temperature will drop slightly.


Clean pipes
Corrosion residues, rust pustules and bioslime are "hiding places" and "food" for the bacteria. When pasteurizing a system, the bioslime can protect Legionella bacteria from the high water temperature.


Good distribution of the hot water
With proper hot water regulation, the recommended temperatures can be maintained.


Correct circulation rate makes it harder for bioslim to develop and adhere, and corrosion protection gets better conditions.


Tank size
The hot water consumption should correspond to emptying the tank 1.5 to 2 times a day. Too large a tank means too long a residence time of the water in the temperature range 20-40 °C. Too small a tank means a risk of thermophilic bacteria due to a lack of layering in the tank.

If it is possible to run a Legionella program (temperature gymnastics) on the water tank, this should normally be done at least once a week. The program should be run at night to avoid scalding injuries.


Dead pipe ends
Improperly plugged pipe ends provide good conditions for bacteria because the temperature is lower and there is no flow in the closed pipe section.


Infrequently used t aps are basically the same as dead pipe ends. Except that you occasionally tap water from there that may have been stagnant for 14 days or more.

All taps should be activated once a week on the highest heat. For the taps that are not activated at normal consumption, you must create an artificial consumption and also remember to exercise the mixer tap so that it does not settle at the preferred bathing temperature.

Do you have any questions? We're ready with advice and guidance

Use our chat function on this page or contact us on +45 48 13 44 00 if you have any questions or would like a visit from our consultants.

Our service centre is also in contact with our service vans if you need service for your installation or emergency assistance.