There’s more to water clarity than chemistry: the art of pool care
4.4.2026
Martin Býšek
Many pool owners believe that water care is a simple routine, much like topping up salt in a dishwasher. We often hear the view that it’s enough to „drop in a tablet and switch on the filtration“. The reality, however, is far more complex. Water is a living system, and keeping it crystal clear requires continuous attention - or a sophisticated technological system that keeps watch on your behalf. Water in an open system is constantly affected by its surroundings - from temperature fluctuations to organic matter introduced by swimmers. Pool care is an ongoing balance between control and natural processes, leading either to a perfectly clean, sparkling surface or, within a short space of time, to unappealing green water resembling a forest pond.
The first prerequisite for crystal-clear pool water is cleanliness. If we don’t learn to keep the pool clean, we can never succeed. The pool will gradually begin to resemble that same forest pond.
A clean pool doesn’t just mean that no debris is floating in the water - such as plant matter from the garden, drowned insects or the remains of our children’s snacks. It’s also about the pool walls being smooth and clean, free from limescale deposits or algae. The same applies to the overflow channel and buffer tank, as well as to the internal parts of the skimmer body. So everything is clean and you think you’re done? I’m afraid not - there’s still more to do. The final step is to check the filter and make sure everything is in order there as well. If you have cartridge filtration, you need to dismantle the filter housing and insert a new cartridge. If your pool includes sand filtration, the process is slightly more involved, but still not difficult. Sand filters have a sight glass that allows you to see inside - and this is exactly where you can check whether the filter is clean. Switch the filtration to backwash mode and start it. You'll immediately see in the sight glass how clean the inside really is. The more curious may even shine a light inside. Leave the filter in backwash mode for as long as the sight glass shows that the water is still full of impurities. Once the water runs clear and only the sand is visible, you’re done. The filter is clean.
What values do we need to maintain?
The question now is how to keep the water clean for as long as possible. Our goal is to keep several water parameters within a defined range. These are mainly pH and the disinfecting capacity of the water. It is essential to maintain pH within the range of 7.0-7.4, while in terms of disinfection, it depends on what your tester is able to measure. In general, there are two options: free chlorine or redox potential. Free chlorine should be maintained within the range of 0.3-0.6 mg/l, while the required range for redox potential is 700-750 mV.
Everything cleaned - what next?
You’ve cleaned the entire pool, including the balancing tank. The pool is filled with clean water, and the filter has been backwashed. Now it’s time to check the water against the parameters we are monitoring. First, measure the current pH value and, if necessary, use products to increase or decrease it so that it falls within the required range. Next, check the disinfection levels in your pool. The most accessible option is usually a free chlorine tester, so measure this value and then use a disinfectant product to bring it up to the required level. The measured value will most likely be low, and your task will be to raise it to the necessary level.
Once the pool water has been brought into balance, all that remains is to ensure that these values stay as they are. There are two ways to achieve this.
Option one – tablets
Place a floating dispenser with a tablet in the pool. As it gradually dissolves, it keeps the chlorine at an acceptable level. However, tablets usually do not stabilise pH. The pH needs to be monitored once or twice a week and adjusted if necessary. This is a fairly effective solution, but it inevitably requires your time and attention. If you forget, the water can quickly lose its sparkle during a hot afternoon. If you have the time to devote to your pool and are looking for a functional solution with minimal initial investment, this is the right choice for you.
Option two – automatic dosing system (pH and chlorine)
This is an electronic system that continuously monitors pH and free chlorine, or redox potential, using sensors, and automatically doses the required amount of liquid agents to regulate pH and disinfect the water so that the monitored values remain optimal at all times. A major advantage of this solution is that, as long as the system has a sufficient supply of liquid chemicals, it can operate independently for a long period of time. If you forget to refill the necessary chemicals, you'll soon notice a drop in water quality. With an automatic dosing system, it's important to calibrate the sensors before start-up and then carry out calibration at the prescribed intervals to ensure that measurements are accurate.
Although the initial investment is higher with an automatic dosing system, you gain a fairly autonomous solution that requires minimal effort, allowing you to enjoy your pool all the more.
A common mistake is starting the system when the water is chemically unbalanced or contaminated after the pool has been shut down for winter or initially filled. Before activating automatic dosing, the water must first be brought to its correct baseline condition.
A sustainable balance
Long-term stable pool water quality is the result of several key factors working together:
- mechanical cleanliness of the pool
- properly functioning filtration
- accurately balanced pH
- sufficient disinfection capacity
If any of these aspects are neglected, reliable and long-term stable operation cannot be expected. Pool maintenance therefore does not begin with the application of chemicals, but with thorough cleaning of the entire system and bringing the water to the correct initial condition. Only then can tablets or automatic dosing systems function effectively. A properly set maintenance regime reduces chemical consumption, minimises operational issues and helps ensure that the water remains hygienically safe, visually clear and stable over the long term.