If you’ve noticed your pool water level dropping, you’re probably asking: is this normal pool water evaporation, or could there be a leak?
In warm climates especially, evaporation is completely natural. However, understanding how much water evaporates from a swimming pool, how to measure it properly, and when water loss becomes a problem can help you avoid costly repairs.
Let’s break everything down clearly.
Pool Water Evaporation Is Calculated Based on Surface Area
One of the biggest misconceptions about evaporation is that it depends on depth. It doesn’t.
Pool water evaporation is calculated based on water surface area. Evaporation happens where water meets air, so the larger the exposed surface, the more water can evaporate.
For example:
- A 15×30 pool (450 square feet)
- Losing ¼ inch of water per day
- Can lose approximately 70 gallons daily
This is why larger pools lose more water, even if they are shallow. A wide pool designed through thoughtful Custom Pool Design planning may have more surface exposure, which can increase evaporation depending on layout and features.
How to Measure Pool Evaporation (The Bucket Test)
Before assuming there’s a leak, you should measure evaporation using the simple and reliable Bucket Test.
How to Perform the Bucket Test:
- Fill a bucket with pool water.
- Place it on a pool step so it sits partially submerged.
- Mark the water level inside the bucket.
- Mark the water level of the pool outside the bucket.
- Wait 24 hours without swimming.
- Compare the water levels.
If both drop equally, the loss is normal evaporation.
If the pool level drops more than the bucket, you may have a leak.
This test helps determine how much water evaporates from a pool in 24 hours versus how much might be escaping due to structural or plumbing issues.
How to Measure and Identify Leaks
If you’re unsure whether water loss is due to normal evaporation or a leak, perform the reliable Bucket Test.
How to Perform the Bucket Test
- Place a 5-gallon bucket on the pool’s top step.
- Fill the bucket with pool water until it matches the pool’s water level.
- Mark the water level inside the bucket.
- Mark the pool’s water level on the outside of the bucket.
- Turn off auto-fill systems.
- Wait 24–48 hours without using the pool.
- Compare both water levels.
If the pool water level drops significantly more than the bucket’s water level, you likely have a leak.
If both levels drop evenly, the water loss is normal pool water evaporation.
Key Factors Driving Evaporation
- Temperature: Higher air and water temperatures increase evaporation rates.
- Wind Speed: Wind removes moisture from the pool surface, speeding up water loss.
- Humidity: Low humidity (dry air) causes faster evaporation.
- Water Temperature: Heated pools lose more water, especially overnight.
- Pool Surface Area: Larger pools lose more water due to greater surface exposure.
- Sun Exposure: Direct sunlight increases surface heating and evaporation.
Proper Weekly Maintenance can also help monitor consistent water levels and catch unusual water loss early.
Pool Water Evaporation Chart (General Estimates)
Here’s a basic evaporation guide:
| Weather Condition | Estimated Daily Loss |
|---|---|
| Mild Weather | 1/8 inch |
| Hot Weather | 1/4 inch |
| Hot & Windy | 1/2 inch |
| Extreme Heat | Up to 3/4 inch |
In warm states like Florida, it’s common to lose 1–2 inches per week in peak summer.
Evaporation Rate Calculator
A pool water evaporation calculator estimates water loss using surface area and environmental conditions.
Basic formula:
Gallons Lost Per Day = Surface Area × Evaporation Depth (inches) × 0.623
Example: 400 sq ft × 0.25 inches × 0.623 = 62 gallons per day
An Evaporation Pool Rate Calculator helps you understand whether your water loss is normal for your climate.
How to Use the Water Evaporation Rate Calculator
To calculate your pool’s evaporation rate:
- Measure pool length × width to get surface area.
- Estimate daily evaporation depth (0.125–0.5 inches).
- Multiply surface area by depth.
- Multiply result by 0.623 to convert to gallons.
For those asking, “What Is My Pool’s Evaporation Rate?”, the answer depends on size and weather. Most residential pools lose 30–70 gallons per day in summer.
How Much Water Evaporates From a Pool in Litres?
To convert gallons to litres:
1 gallon = 3.785 litres
If your pool loses 60 gallons daily:
60 × 3.785 = 227 litres per day
Over a month, that could exceed 6,000 litres in hot climates.
Understanding this helps homeowners plan water usage and maintenance costs.
How to Find a Leak in a Pool
If water loss exceeds normal evaporation, you may need to check for leaks.
Common leak locations include:
- Skimmer cracks
- Return jets
- Light niches
- Main drain fittings
- Tile lines
If you notice water dropping more than 1 inch per day, wet soil around the pool, or constant refilling, professional leak detection may be required.
Pool Pump Leaking at Housing
Sometimes water loss isn’t from the pool structure at all. It may be equipment-related.
A common issue is pool pump leaking at housing.
Possible causes include:
- Cracked pump housing
- Worn O-ring
- Loose plumbing fittings
- Failed shaft seal
Signs of pump leaks:
- Water puddling under equipment
- Air bubbles in return jets
- Reduced water pressure
Addressing pump leaks quickly prevents larger mechanical damage.
FAQs
Why does water evaporate?
Water evaporates when heat converts liquid water into vapor. Sunlight, warm air, and wind accelerate this process.
How to calculate pool water evaporation rate?
Multiply pool surface area by evaporation depth in inches and then multiply by 0.623 to convert to gallons.
How much water evaporates from a pool in 24 hours?
Most pools lose between 1/8 to 1/4 inch daily in warm weather, which equals 30–70 gallons depending on size.
How much water evaporates from a pool in litres?
That typically equals 150–250 litres per day in summer conditions for average-sized pools.
Final Thoughts
Pool water evaporation is completely normal, especially in warm climates. However, excessive water loss may signal a leak or equipment issue.
Monitoring your water level regularly, performing the Bucket Test, and staying consistent with Weekly Maintenance ensures your pool stays efficient and problem-free.
If you’re planning a new Custom Pool Design, factoring in size, shape, and exposure can also help manage long-term evaporation and maintenance costs.
Understanding your pool’s evaporation rate helps you stay proactive and protect your investment.
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