The same water all summer long, new water every day.

You've probably experienced the pungent smell of disinfectant when entering a swimming pool or water play area. We often dismiss it, thinking "they must have disinfected thoroughly," but it can actually be a sign of the opposite. That single smell tells us quite a lot about what's happening in the water.

In the previous installment, we discussed water temperature. This time, we'd like to delve into a topic just as important as temperature, but far less visible: how water is managed. Even if the water looks equally blue and clear on the surface, its condition beneath can vary significantly depending on the management method.

Two Ways to Manage Water

Outdoor water play areas generally handle water in two main ways.

One is the method of circulating and disinfecting the same water. Water is passed through a filter to remove impurities, disinfected with chlorine, and then returned to the pool. Most swimming pools use this method. While it conserves water, the more people who use the facility, the more waste accumulates in the water, requiring continuous addition of disinfectants to manage it.

The other is the method of frequently replacing the water itself. This is only possible if a sufficient supply of fresh water can be secured. It's not common because it's unfeasible if water is scarce, but it can significantly reduce management burden and disinfectant usage.

There are no issues as long as both methods adhere to the water quality standards set by law. However, if children will be spending a long time in the water, it's worth considering which type of water it is.

This difference becomes even more pronounced during peak season when many people visit in a single day. As people pass through, sweat and waste accumulate in the water, and the circulation and disinfection method requires more disinfectant to manage this. In contrast, places that frequently replace the water have less accumulation to begin with, resulting in less burden. Even if water play areas appear equally crowded on the surface, the water's condition at the end of the day can be quite different.

Legal Water Standards

In Korea, swimming pool water quality is regulated by law. According to the Enforcement Rule of the Act on the Installation and Utilization of Sports Facilities, swimming pool water must maintain a turbidity of 1.5 NTU or less, free residual chlorine of 0.4~1.0 mg/L, and must also pass E. coli tests. The water's acidity must be between pH 5.8 and 8.6.

It's perfectly fine if these numbers seem unfamiliar. The key is one thing: a good water play area should regularly test against these standards and be able to disclose the results. Facilities confident in their water management will not hesitate to show their test results.

What the Disinfectant Smell Tells Us

Let's return to the disinfectant smell we discussed at the beginning. The smell we commonly refer to as "chlorine smell" is usually combined residual chlorine. This is a substance formed when chlorine, added for disinfection, reacts with organic matter like sweat or waste, producing its characteristic odor while having weak disinfecting power.

In other words, a strong smell is less a sign of extensive disinfection and more an indication that there was a significant amount of material in the water that needed to be treated. The law also stipulates that this combined residual chlorine should be managed at 0.5 mg/L or less. If your eyes sting and the smell is pungent when you enter a water play area, it's worth considering the condition of the water that day.

The Ability to Use Fresh Water

To summarize: The more frequently water is replaced, the less waste accumulates in the water, and the less reliance there is on disinfectants. However, this is only possible when a sufficient supply of fresh water can be secured.

Undam Park has a somewhat special environment in this regard. A significant amount of water emerges from the ground here every day. Thanks to this, we are planning a method of filling the water play pools with fresh water every morning. This means that instead of circulating the same water throughout the summer, we can choose to replace it daily. We will continue in the next installment to explain where and how this water emerges.

What's in the water isn't fully visible to the eye. Therefore, when choosing a water play area, we recommend asking questions instead of just looking at photos. "How often do you change the water?" and "Do you conduct water quality tests?" With these two questions, you can generally gauge how the water is managed. If you receive good answers, your water play experience for the day is already halfway to success.