Tiny Sensors Help a Major Hotel in Germany be Legionella Compliant and Save Costs Within Days

Tiny Sensors Help a Major Hotel in Germany be Legionella Compliant and Save Costs Within Days

Morten Gamre
19. Jul 2022 | 11 min read

Tiny Sensors Help a Major Hotel in Germany be Legionella Compliant and Save Costs Within Days

One of the challenges that all building owners face is the constant effort to prevent legionella bacteria in the water supply. Legionella is a water-borne bacterium that can cause Legionnaire’s disease, a lethal respiratory illness. Preventing the bacteria from multiplying and remaining compliant with local and national rules and regulations is extremely important for building owners and landlords. But it can also be very costly.

A large real estate company in southern Germany is using IoT sensors from Disruptive Technologies (DT) to face this challenge. They own multiple properties, including hotels, office buildings, and apartment blocks. Their portfolio also includes a major hotel with over 1,100 rooms and apartments spread across 23 floors. 

The hotel, which was built in the late 1960s, has a sophisticated water system that provides both hot and cold water and has 12 risers spread across three different pressure zones. Some of the levels exceed a length of 150 meters. This system supplies water to residential guests, restaurants, clinics, and offices.


Facts about Legionella 

The legionella bacteria is present in all untreated water but usually in such small concentrations that it is harmless to humans. Typically, in 1 cubic meter of water, there are between 4 and 6 Colony Forming Units (CFU) of legionella. Approximately 600 CFUs enter the building every day, an acceptable number under normal conditions.


However, if water remains stagnant and tepid for a prolonged period of time at a temperature between 18 and 48 degrees Celsius (64.4 and 118.4 degrees Fahrenheit), the bacteria will grow. If left untreated, it expands to a critical mass, large enough to infect humans through aerosolized water (microscopic water spray), surging from taps, showers, air conditioning units, and any other appliance using water. This can lead to a serious illness that, in some cases, is fatal.

It is therefore critical that building operators undertake appropriate preventative measures to avoid any buildup of this potentially fatal bacteria. This presents a significant challenge, and the common solution is to regularly flush all the taps, which is very labor-intensive and wasteful.


What were the identified challenges?

The hotel had identified a number of issues with its complicated water system, including:

  • Stagnant water in the pipes can lead to the build-up and spread of the Legionella bacteria
  • Variations in water temperature between different locations in the hotel
  • Adjusting water temperature and/or water pressure in one area affects water temperature and/or water pressure in other parts of the hotel
  • The need to comply with German Health and Safety legislation, which requires documented proof that water temperature measurements are regularly conducted.


Sensors provided a solution

To investigate and resolve these issues, the hotel’s landlords employed the services of WATERplus, a company that brings together its competence and experience in water management systems for buildings. They specialize in microbiology and chemistry and further apply their technical expertise in technology to provide a practical solution to establishments that must adhere to the Legionella regulations. 

In addition to expertise in implementation, WATERplus has considerable knowledge of the country’s legal requirements and regulations concerning buildings’ water management. The company acts as an intermediary between the water operator and the end-user or consumer, as an arbitrator between the installer and the client, and as a consultant to the real estate industry.



In 2021, WATERplus deployed Wireless Temperature Sensors from Disruptive Technologies to help calculate water temperature in the pipes of the hotel. They selected DT sensors for the following reasons:

  • Peel and stick: The sensor comes with a strong adhesive that lets you attach the sensor exactly where you need it. All you have to do is peel and stick the sensor. No technical expertise is required.
  • 24/7 monitoring:  The sensors are reporting temperature levels every 15 minutes
  • Tiny size: 19 x 19 x 2.5 mm, the smallest in the world
  • Long battery life: Proprietary technology allows most sensors to work for up to 15 years in the default configuration.
  • Affordable: DT offers the lowest cost per insight in the IoT sensor market.



Specifically, WATERplus chose the standard DT temperature sensors for monitoring the cold water and the Industrial Wireless Temperature Sensors for monitoring the hot water. The industrial version is better suited for measuring higher temperatures.

WATERplus has currently distributed 76 wireless sensors and 8 Cloud Connectors throughout the hotel, including:

  • in the basement, where the water enters the building and is heated. The water pressure and temperature are also controlled from here.
  • on water pipes on each floor.
  • in some of the apartments.


The sensors are installed exactly where they are needed and allow WATERplus and the hotel owner to monitor the water temperature throughout the hotel.

Waterplus has combined their own building management software, BlueBook, with DT Studio to get a user-friendly graphical interface that provides easy-to-read data on the temperature recorded by each sensor over time.

Studio water plus 1Diagram showing temperature over time for one pipe on the 5th floor.

By analyzing the data from the sensors, WATERplus is now able to:

  1. identify pipes where the water temperature has remained stagnant for too long, and so could become a breeding ground for the Legionella bacteria
  2. assess variations in water temperature at different locations within the building, making adjustments to the physical water system to get a more even distribution
  3. quickly understand how any adjustments that are made to the water pressure or temperature affect other areas 
  4. provide historical data showing water temperature at each location over time
  5. see the effects of the flushing routines, including when they are performed
  6. conduct an investigation into the cause of a Legionella outbreak and the location of the problem.


By analyzing the results, the building owner is able to make decisions based on real data and then see the results of the measures taken to solve the issues.

Landlords need to document the water temperature in pipes to comply with the German regulations regarding legionella. This used to be done manually, but now, with the use of sensors, the task can become a lot simpler and more cost-effective. The administration, analytics, and reporting of the temperature data can be done with the help of the software, where the sensor data is kept safe from manipulation. 

When a pipe has been identified as being a potential location for the growth of Legionella, two options are available for rectifying the potential problem:

  1. disinfecting the water
    Disinfecting the water is both costly and time-consuming and therefore not feasible.

  2. flushing the affected pipes
    Flushing the affected pipes is currently being undertaken by a service company. Every 72 hours, they physically flush both hot and cold water pipes in all rooms where the water has not been used. This takes 3 minutes per pipe. Each hot and cold flush uses 30 liters of water, potentially wasting a maximum of 66,000 liters every 72 hours. This is not sustainable and very costly in terms of both water costs and wasted energy on heating.


iStock-1074899602Manually flushing pipes to measure the water temperature. 

Automatic flushing has been considered, but is not practical and would be expensive.

Using data from the temperature sensors, the hotel and WATERplus staff can easily identify which pipes actually need flushing, which results in:

  1. a reduction in the volume of wasted water
  2. cost savings associated with:
    i)  using less water
    ii) spending less time manually completing the activity
  3. energy savings as less water requires heating
  4. reduced carbon emissions as a result of less heating


What are the next steps?

In an ideal world, WATERplus would install a filter on the incoming water supply to prevent the legionella bacteria from entering the hotel pipes. This would completely remove the need for flushing the pipes. However, this is unfavourable due to the age of the building and the cost of filters. 

For a building free of the legionella bacteria, the temperature of the hot water can be reduced (i.e., from 60 degrees to 45 degrees). This saves energy and money, as well as reduces the carbon footprint of the building. This scenario is under consideration, so for now, they are very satisfied with the sensor solution and all the benefits they get from it.

Whether a filter is installed or not, the DT sensors will be retained to assist with water flow adjustments, energy savings, and ensure the appropriate water temperature for all of the hotel guests. The sensor data would also be used to create legionella reports for the authorities.


Get in touch with us

Morten Gamre

Morten Gamre

Morten is the Partner Marketing Manager at Disruptive Technologies. He has 20+ years of valuable Marketing experience from various tech companies. He holds a degree in International Marketing and Management from BI Norwegian Business School. Morten works closely with and supports our global partners towards making all buildings smart & sustainable with our tiny sensors. Outside of work, he enjoys music, kayaking and spending time with his two boys.

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