💧 Pool Water Loss Caused by Evaporation and Backwash

💧 Is Your Pool Leaking Water, or Is It Evaporating?

Is your pool’s water level constantly dropping, but you’re not sure why? Especially during hot summer months, many pool owners ask themselves, “Is my pool leaking?”

However, in most cases, this drop is not caused by a leak that should cause panic, but by a completely natural process called evaporation. Factors such as air temperature, wind, humidity level, and sun exposure can cause pool water to decrease faster than expected.

In this article, we will help you understand the real cause of water loss by explaining the differences between evaporation and leakage, simple testing methods, and the correct solution approaches step by step.

1. What Is Evaporation and How Does It Occur?

Evaporation is the process by which water changes from liquid to gas and moves into the atmosphere, and it is one of the most fundamental physical cycles in nature. Although invisible, it is one of the primary causes of water loss, especially in open-surface pools.

The rate of evaporation is directly affected by many environmental factors such as solar radiation, air temperature, wind speed, relative humidity, and the size of the water surface. On sunny days, the water surface warms up, molecules gain energy, and with this increased energy, water turns into vapor and mixes with the atmosphere.

Wind accelerates evaporation even further by continuously removing the humid air layer formed on the surface, allowing new molecules to escape into the atmosphere. Similarly, low humidity increases evaporation because dry air absorbs water vapor more rapidly.

As a result, especially during summer months and in dry climate regions, a decrease of several millimeters or even centimeters in pool water level due to evaporation is completely normal. However, without regular monitoring, these natural losses can turn into significant water and energy waste over time.

• High temperature = faster evaporation
• Low relative humidity = air absorbs more water vapor
• Wind = removes evaporated moisture and accelerates the process
• Large surface area = more evaporation surface

On average, an open-surface pool can lose 5–12 mm of water per day. This corresponds to hundreds of cubic meters of water annually for a 100 m² pool.

2. Evaporation or Leakage?

The most practical way to answer this question is the “bucket test.” This easy-to-apply test clearly shows the cause of water loss.

How Is the Bucket Test Performed?

1. Fill a bucket with pool water and place it on the pool steps or edge so that the water level matches the pool’s water level.
2. Mark the water level in both the bucket and the pool.
3. Leave it overnight and check the levels in the morning.
4. If both water levels drop by the same amount → it is evaporation.
5. If the pool water level drops more → there may be a leak.

This test should be carried out in a windless environment and away from direct sunlight. The results usually provide a clear indication within 24 hours.

3. How Much Water Loss Is Normal?

The evaporation rate varies depending on climatic conditions:

These values may correspond to a total annual water loss of 300–500 m³ from the pool surface.

4. Factors That Increase Water Loss

• High temperature: Evaporation rate can double under direct sunlight.
• Low humidity: Dry air absorbs water more rapidly.
• Wind: Removes evaporated moisture from the surface, increasing water loss.
• Uncovered pool surface: Water loss can increase by up to 50% in uncovered pools.

5. Ways to Reduce Water Loss

• Use a pool cover: Covering the pool at night can reduce evaporation by up to 70%.
• Automatic cover systems: Closing during sunny hours saves both water and energy.
• Wind barriers: Especially effective for outdoor pools to reduce evaporation.
• Regular maintenance: Check filters, pipes, and skimmer lines for leaks.
• Liquid evaporation barriers: Invisible film layers slow down evaporation.

6. When Should You Call a Professional?

If the bucket test shows that the pool water level is dropping more than the bucket, this may indicate a leak or connection problem. Professional inspection is required in the following cases:

• Cracks on the pool floor or walls
• Sudden pressure changes in the filtration system
• Water leakage around skimmers, nozzles, or lighting fixtures

With professional leak detection, you can minimize both water loss and energy costs.

Conclusion

A drop in your pool’s water level does not always indicate a malfunction or leakage; in most cases, especially in hot, dry, and windy climates, it is the result of evaporation—a completely natural process. Sunlight and wind accelerate water molecules on the surface, causing them to disperse into the atmosphere and leading to noticeable water loss. What truly matters is correctly distinguishing between evaporation and a potential leak. To do this, you can apply the simple yet effective bucket test, monitor the water level for several days, and seek professional support if you have doubts. With proper analysis and regular maintenance, you can manage your pool’s water more efficiently, prevent unnecessary water waste, and significantly reduce long-term maintenance costs.

Artemis Pool & Fountain Systems — Scientific, aesthetic, and sustainable pool solutions.