At Rosenau outdoor swimming pool, water quality is tested twice a day in each pool for pure, carefree fun
August 2025 had everything – the sun was shining, temperatures hit new highs, and the air shimmered in the heat. For many people at JUMO’s headquarters in Fulda there is only one place that makes this heat bearable: Rosenau outdoor swimming pool in the center of the cathedral city. Children joyfully splash about in the pool while adults relax and enjoy swimming laps or simply relish the cool water. The atmosphere at the edge of the pool and at the snack bar is very light and easy. However, while the summer visitors enjoy themselves, a complex interplay of technology and many years of technical knowledge occurs in the background. This interplay ensures the safety and wellbeing of everyone by performing the important task of monitoring and managing the water quality.
"On hot days like this which are over 30 °C, we change some technical settings. We have to rely on the technology here," says Michael Lipus, Head of BäderBetriebs GmbH (BBG). BBG belongs to the supplier RhönEnergie in Fulda. RhönEnergie is one of the 20 biggest municipal energy suppliers in Germany. BBG now operates 8 outdoor and indoor swimming pools in the Fulda district and in the town of Schlüchtern.
Water quality: more than just clear H2O
Ensuring a constantly high level of water quality is one of the key tasks at the Rosenau outdoor swimming pool. Both the well being and the health of the pool guests are key here. After all, only perfect water quality will protect against infection, skin irritation, and other health risks. "Monitoring and management of important water parameters such as pH value, chlorine content, redox potential, and water hardness are essential here," states Lipus, based on his many years of experience.
Rosenau outdoor swimming pool is the largest open-air swimming pool in the Fulda district. It was inaugurated in1938, given a general overhaul for the first time in the 1960s, and the entire pool facility was refurbished in 2007. The total quantity of water in all 4 pools (including the children's paddling pool) is now 4078 m³, and the total water surface 2457 m².
The Rosenau outdoor swimming pool relies on vertical flow. The clean water is introduced into the bottom of the pool through clean water ducts in this process. "The dirty water is discharged via the overflow channel," explains Lipus. Corresponding nozzles are required in the bottom of the pool to ensure even water distribution.
Modern measurement technology: Precision and automation
The pH value is the centerpiece of water quality. Ideally, it is between 6.5 and 7.5. If the pH value is too low, i.e., too acidic, the chlorine used is consumed too fast and metallic components (such as filter systems) may be corroded. "On the other hand, if the pH value is too high, the chlorine loses its disinfecting effect, which can result in the water turning green and limescale deposits," states Matthias Kremer,Water and Wastewater Industry Manager at JUMO.
Monitoring of the chlorine content is also essential, as chlorine is used as a primary disinfectant. Optimal dosing ensures reliable germ elimination while preventing unwanted side effects like skin or eye irritation.
Another key parameter is redox potential. It indicates in millivolts (mV) how strong the germicidal effect of the disinfectant is in water. A stable redox value is a reliable indicator of water quality and the effectiveness of disinfection. Water hardness also plays a role, as it impacts the dispensing of chemicals and the formation of deposits.
JUMO has been successful in the field of water and wastewater for many years
For years, one of JUMO's success stories has been the JUMOtec Linep Hand redox electrodes – high-precision sensors for continuous monitoring of the pH value and redox potential in pool water, as Kremer explains further. They provide reliable measured values and are particularly durable. JUMO also acts as a supplier which means that the sensors are sold by other companies under their respective labels. Continuous measurement and automatic control of these values is ‘state-of-the-art’ so that efficient and safe swimming pool operation is ensured. Modern systems enable operators to monitor water quality round the clock, to identify deviations right away, and counteract them specifically – often even fully automatically. Overall, 1460 m³ of water is circulated every hour at Rosenau outdoor swimming pool in full-load operation.
Technology has made a giant leap forward in 40 years
determined quickly
"Technology for outdoor and indoor swimming pools has made a giant leap forward over the last 40 years," Lipus says from experience. Nowadays he can only chuckle when he thinks back on the requirement in the 1970s and 1980s to wear bathing caps in swimming pools. "Today, there are filters that effectively fish out pollutants." Nevertheless, it is very important for good water quality that pool users take a quick shower before they go swimming or splashing around.
"When the sun is really beating down and there are a lot of guests in the pool everyday, the redox values fall. We then readjust the chlorination," Lipus explains further. The redox potential is a value for the germicidal effect of disinfectants in swimming pool water.
The higher the potential, the harder it is for micro organisms in the water to survive. So, the higher the potential, the cleaner the water. At Rosenau outdoor swimming pool, water quality is tested twice a day in each pool.
Safe and cost-effective pool operation
determining the pH valuePhoto captions 1/2/3: The
Rosenau outdoor pool in the center of Fulda
BBG can use a mixture of systems and solutions to reliably monitor the water quality in Rosenau outdoor swimming pool, automate cleaning and disinfection processes, and therefore ensure safe and cost-effective operation. "Here, visitors can enjoy the refreshing water without any worries – and can rely on us to ensure their safety behind the scenes using state-of-the-art technology. This ensures that their visit to the outdoor swimming pool becomes a genuinely enjoyable experience, even on the hottest days," Lipus concludes.
JUMO solutions for water and wastewater technology
As a specialist in measurement and control technology, JUMO offers a wide range of products and systems which have been especially developed for the field of water and wastewater or for use in swimming pools:
➊ JUMO tecLine pH and redox electrodes: High-precision sensors for continuous monitoring of pH value and redox potential in swimming pool water. They provide reliable measured values and are particularly durable.
➋JUMO AQUIS touch S/P: A modular multichannel measuring device that enables all relevant water parameters such as pH, redox, chlorine, conductivity, and temperature to be measured, controlled, and visualised. The intuitive operation and flexible expansion options make it the centerpiece of modern water treatment.
➌JUMO tecLine Cl02: Robust sensors for measuring free chlorine, total chlorine, and other disinfectants. They are especially designed for use in demanding environments and ensure precise monitoring of the disinfectant concentration.
➍JUMO variTRON: The JUMO variTRON system can be used effectively for quality control in the field of water and wastewater. Thanks to the modular automation platform, various sensors and measuring devices for monitoring parameters such as pH value, conductivity, temperature, oxygen content, and turbidity can be seamlessly integrated. The acquired measurement data is processed and visualised centrally, and can be documented automatically. This way, JUMO variTRON provides gapless monitoring of water quality.
