Water Quality and Kombucha Fermentation: An Interview with Leogant Founder Thomas Hartwig
The composition of the water used can affect the taste of tea and potentially the course of kombucha fermentation. Whether additional filtration makes sense depends on the quality and composition of the source water, as well as the filtration system used. In our interview, Leogant founder Thomas Hartwig talks about water quality, water filtration, and his experiences with water when fermenting at home.
The Path to Founding Leogant: A Portrait of Thomas Hartwig
How did you come up with the idea to found Leogant? Please introduce yourself briefly!
I founded Leogant about 12 years ago. Founding the company was much more than just a business case. It was more of a life's mission, always with a very clear focus on conscious business with purpose. From the very beginning, there was a clear purpose: to give people a good feeling about good water. The business model was rather in the background. I am a trained restaurateur and later studied the Asian martial art of Kung Fu in China. I have always had an affinity for high-quality food and a good sense of how my body feels. Back in Berlin, I continued to focus a lot on nutrition and sports and ate a vegan diet. After working out for 6 hours a day, I quickly noticed how much more capable my body was with high-quality spring water from the organic market. Water quality thus became a central topic for me—both in terms of taste and in the selection and preparation of my drinking water.
Actually, it goes without saying, because our bodies and our planet consist largely of water. Water is also very interesting from a scientific perspective. No substance has so many properties and anomalies that science cannot explain. With the founding of Leogant and our water filtration systems, I have developed a sustainable and holistic solution to address people's individual needs, and I want to bring the importance of water for our organism more into focus. All this with a sustainable business without compromises.
How does the LEOGANT filter work?
I packed the first packages with water filters myself back then in my 20-sqm office. For this, I collected boxes from everywhere to work as sustainably as possible. This sustainability, which was not yet so fashionable back then as it is now, is still reflected in our filtration systems today. All the components of the water filters are already existing products. From the very beginning, I examine exactly what the market already offers, take apart the existing systems, see how I can improve them, and put them back together as newly combined water filters.
The 2-Phase Filtration System
Leogant describes its system as a two-stage water treatment. In the first stage, activated carbon filters are used, among others. Which substances are reduced during this process and to what extent depends on the specific filtration system and its tested filtration performance. The provider refers to the second stage as "revitalization". What objectively measurable changes are associated with this can only be assessed on the basis of the technical evidence of the respective system.
What happens to the lime in the water?
The lime content is often viewed critically. Calcium and magnesium are minerals that can occur naturally in water and also influence its taste. Therefore, it is not fundamentally necessary to remove lime from drinking water. Whether a reduction in water hardness makes sense depends, among other things, on the desired taste, the use, and the process employed. Which minerals remain in the water or are reduced should be assessed based on the properties of the respective filtration system.
Have you dealt with kombucha before?
I have been a big kombucha fan for years and was even a speaker at the first Kombucha Summit. The kombucha community is super inquisitive and has a remarkable cohesion. I sometimes miss that with the water experts. For a good kombucha, water quality plays a role. Differences in the source water can affect the taste. I work with several Berlin kombucha manufacturers, and we install our Leogant water filters in their kombucha breweries. It is super exciting to accompany the manufactories on their journey and to help influence their various kombucha flavors.
What differences can filtered water make in kombucha fermentation?
Tap water: filtered or unfiltered?
In my opinion, a clear distinction should be made between water for machines and drinking water for humans. The waterworks provide a great service that allows us to access clear water at any time in everyday life. Nevertheless, treated tap water is not automatically identical to natural spring water. If you consider water as food, it is worth looking into its origin, composition, and taste.
- What options are there? I can buy bottled spring water or treat my tap water with a suitable water filter. Whether additional filtration is necessary or makes sense depends on the local water quality and the desired result.
- What changes through filtration? Depending on the filtration system, the composition of the water can change. Which substances are reduced and to what extent depends on the filter and its tested performance. Whether the taste or fermentation process changes also depends on the source water quality and the other fermentation conditions.
Effects of "revitalized" water on kombucha
Water composition and filtration can affect the taste of the tea and thus also change the taste foundation for kombucha. How a specific water affects SCOBY growth, acid development, or the fermentation process depends on several factors, including the composition of the water, the culture, the temperature, and the fermentation duration. A blanket statement that "revitalized" water improves kombucha or protects against mold cannot be derived from this.
How does filtered water affect the taste of kombucha?
The water composition can affect the taste of tea and thus also the taste foundation for kombucha. Here, water hardness and mineral content play a role, among others. However, there is no hardness level that is equally optimal for all teas and kombucha recipes. The statement that softer water automatically leads to more sour kombucha cannot be generalized either. For a reproducible result, it is worth keeping the water source and the other fermentation conditions as constant as possible.
Tips on water quality for fermenting kombucha at home
- Use fresh water: If drinking water has been sitting in the pipes for a long time, it may be useful to let it run until it becomes noticeably cooler. The instructions of the local water supplier are authoritative in case of questions about water quality and household plumbing.
- Choose a filter suitable for the purpose: Boiling and a coffee filter do not replace a water filter with defined filtration performance. A coffee filter can retain visible particles, but it cannot reliably remove dissolved substances or water hardness. For kombucha fermentation, suitable drinking water is fundamentally crucial.
- Keep water carafes hygienic: Semi-precious stones such as rock crystal, amethyst, and rose quartz are sometimes used decoratively in water carafes. An improvement in water quality through such stones is not reliably proven. If you use them as decoration, make sure that they are expressly suitable for contact with drinking water and easy to clean.
- Trace water quality: Tap water and bottled water are subject to different legal requirements and control systems. In Germany, tap water is generally of very good quality and is comprehensively monitored. You can get information about the local water composition from your water supplier. More on drinking water quality at the German Environment Agency.
A strong water community as a future vision
What is your personal mission for the future?
In my post-Leogant vision, after 12 years in the "water business", I simply want to stand at the meta-level for the whole exciting water topic. I want to build a strong water community, because together is always better than against each other. I would also like to develop great concepts around the topic of water with competitors and sensitize people to the topic.
The most important things at a glance
- The composition of the water can affect the taste of the tea and thus also the taste of kombucha.
- A water filter is not fundamentally necessary. Whether it makes sense depends on the source water quality and the specific filtration system.
- Water hardness and mineral content are not alone decisive for the success of a kombucha fermentation.
- "Revitalization" should not be equated with a proven improvement of the fermentation or protection against mold.
- For a successful fermentation, in addition to suitable drinking water, hygiene, a suitable starter liquid, the culture, and controlled conditions are important.
Frequently asked questions about water quality and kombucha
Do I need to filter tap water for kombucha?
No, not fundamentally. Tap water in Germany is generally of very good quality. Additional filtration can be an option depending on the source water and desired taste, but it is not generally required for kombucha fermentation.
Does water hardness affect the taste of kombucha?
Yes, water hardness and mineral content can affect the taste of the brewed tea. How clearly this affects the finished kombucha depends, among other things, on the tea, culture, and fermentation conditions.
Is revitalized water better for the SCOBY?
A generally valid scientific basis that so-called revitalized water fundamentally makes the SCOBY grow better or improves the fermentation cannot be assumed. Suitable drinking water and hygienic, controlled fermentation conditions are crucial.
Can water filtration prevent mold in kombucha?
No. Water filtration is not a reliable protection against mold. Pay attention to clean equipment, sufficient suitable starter liquid, and suitable fermentation conditions. In case of visible mold, you should discard the entire affected batch.
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