The Truth About Pool Evaporation And How To Minimise It
If you’ve ever wondered why your pool water level seems to drop even when there’s no obvious leak, the answer is simple: evaporation. Pool evaporation is a normal process, but it can be surprisingly costly over time — not just in lost water, but also in added energy bills, increased chemical use and more maintenance. Understanding how and why evaporation happens can help you take practical steps to reduce it. This guide will break down the causes of pool evaporation, how much is considered normal, and most importantly, how to minimise it without compromising your pool’s comfort or usability.
What Is Pool Evaporation?
Evaporation is the process where liquid water turns into vapour and escapes into the air. In your pool, this occurs when water on the surface absorbs enough heat energy — from the sun, air or even wind — to transition into gas.
This process is continuous and influenced by several environmental and mechanical factors. Left unchecked, it can result in thousands of litres of water loss each year.
How Much Water Do Pools Lose To Evaporation?
On average, an uncovered backyard pool can lose between 2.5mm to 5mm of water per day due to evaporation. That can add up to 100–150 litres per square metre per week — depending on your pool’s size, that’s hundreds or even thousands of litres every week.
In hot, dry or windy areas (such as parts of regional Queensland or inland New South Wales), evaporation can be even more extreme. Heated pools and those with high surface area relative to volume are also more prone to rapid loss.
Key Factors That Increase Pool Evaporation
Several environmental and operational factors influence how quickly your pool loses water:
1. Temperature
The warmer the air and the water, the faster evaporation occurs. Heated pools are especially vulnerable, especially if used year-round.
2. Humidity
Dry air accelerates evaporation. When the surrounding air has low humidity, it absorbs moisture from your pool more quickly.
3. Wind
Air movement over the surface of the pool removes the moist air layer and replaces it with dry air, speeding up evaporation. Windbreaks or fences can significantly reduce this effect.
4. Sun Exposure
Direct sunlight heats the water and encourages surface evaporation. Pools in full sun for most of the day will evaporate faster than shaded ones.
5. Surface Area
The larger your pool’s surface area, the more space there is for water to evaporate. Shallow or wide pools lose more water than deeper, more compact ones.
6. Usage
Heavy pool use introduces splashing and increased surface agitation, both of which contribute to faster evaporation.
How To Tell If It’s Evaporation Or A Leak
It’s important to distinguish between natural water loss and a leak. A simple test is the bucket test:
Fill a bucket with pool water and place it on a step so it’s partially submerged.
Mark the water level inside and outside the bucket.
Leave it for 24–48 hours (without rain or topping up).
If the pool level drops significantly more than the bucket level, you might have a leak.
How To Minimise Pool Evaporation
Now that we know what causes evaporation, let’s look at how to manage it. These solutions range from simple adjustments to long-term investments, but all contribute to reduced water loss and greater pool efficiency.
1. Use a Pool Cover
A high-quality pool cover is one of the most effective ways to cut evaporation — by up to 90% in some cases. Choose from:
Solar covers: Trap heat and reduce evaporation.
Thermal blankets: Help retain heat and prevent water loss.
Automatic covers: Convenient and effective, though more expensive.
If you swim daily, consider a roller system to make daily covering easier.
2. Install Windbreaks
Strategically placed barriers reduce air flow across your pool’s surface. These can include:
Privacy screens
Glass or timber fencing
Hedges or shrubs
Ideally, windbreaks should be tall enough to block prevailing winds but not so close as to reduce airflow completely (which can lead to other moisture issues).
3. Shade Structures
Adding shade over your pool reduces heat absorption and slows down evaporation. Popular options include:
Shade sails
Retractable awnings
Pergolas
These also improve swimmer comfort and help protect your pool finishes from UV damage.
4. Lower Pool Temperature
If you heat your pool, consider reducing the set temperature when not in use — even a few degrees can make a difference. Turn off heating completely when the pool won’t be used for extended periods.
5. Manage Water Features
Fountains, waterfalls and bubblers increase water movement, which speeds up evaporation. You don’t need to eliminate them, but turning them off when not in use can significantly reduce water loss.
6. Check for Automation Settings
Automated pool systems sometimes run heating or pumps more than necessary. Optimise run times and settings based on season and usage.
7. Cover Spa Areas Separately
If your pool includes a spa, cover it separately when not in use. Spa water is usually warmer, which means it evaporates faster than the rest of the pool.
Other Benefits Of Reducing Evaporation
Minimising evaporation isn’t just about saving water. It also has flow-on benefits that can save you time and money in the long run:
Lower chemical usage: Fewer top-ups mean more stable water chemistry.
Reduced energy bills: Less heating required when water loss is minimised.
Less maintenance: Reduced debris and algae growth when a cover is used.
Environmental impact: Helps conserve water during droughts or restrictions.
Final Thoughts
Pool evaporation is a natural but often underestimated issue for pool owners. While you can’t stop it entirely, understanding the causes allows you to take practical steps to minimise it.
Whether it’s installing a pool cover, adjusting heating habits or adding a shade sail, small changes can make a big difference. Not only will you save water, but you’ll also enjoy a more efficient, cost-effective and environmentally responsible pool.
If you’re planning a new pool or looking to upgrade, speak with your pool builder about design features that help reduce evaporation from day one.
To get your pool, GET A QUOTE HERE to start your journey with us at Barrier Reef Pools Perth.
