When a pool begins losing water, the first step is determining whether the loss is due to normal evaporation or an actual leak.
Most pools lose water naturally. However, water loss that exceeds expected levels is often a sign of a problem within the pool or plumbing system, and should not be ignored.
This page outlines what’s considered normal, how to evaluate water loss, and when further testing should be considered. If you’re unsure whether your pool is actually leaking, it helps to first understand the most common signs your pool may have a leak.
What Is Normal Pool Evaporation?
Most swimming pools lose some water due to evaporation, but the amount can vary depending on conditions like sun exposure, air temperature, wind, humidity, and water temperature. Under typical conditions, it’s common to see water loss in the range of about 1/8” to 1/4” per day, which adds up to roughly 1 to 2 inches per week. When water loss approaches or exceeds around 2 inches per week, especially without extreme weather conditions, it may be more than just evaporation. Consistent or excessive water loss beyond this range should be looked at more closely to determine if a leak may be present.
How Much Pool Water Evaporates in New Jersey and New York?
Pool evaporation in New Jersey and New York changes throughout the season. There is no single daily rate that applies to every pool because temperature, humidity, wind, direct sunlight, water temperature, and pool use all affect how quickly water evaporates.
During the warmer summer months, a swimming pool may lose approximately 1/8 to 1/4 inch of water per day under typical conditions. Hot, dry, or windy weather can increase evaporation, particularly when the pool receives direct sunlight throughout the day.
During spring and fall, cooler daytime temperatures do not necessarily eliminate evaporation. Heated pools can continue losing noticeable amounts of water, especially when warm pool water is exposed to cool, dry nighttime air.
In late fall and winter, evaporation from an uncovered pool generally decreases as water temperatures fall. A properly covered pool should experience substantially less evaporation because the cover limits the amount of water exposed to moving air.
These figures are useful guidelines, but weather conditions vary too much to diagnose a leak based on an evaporation average alone. If you’re regularly losing 1/2 inch, 1 inch, or more per day, or simply want to compare your pool against evaporation at your own property, the best next step is a pool leak bucket test.
When Water Loss May Indicate a Leak
Evaporation tends to happen at a steady, predictable rate, so when water loss starts to exceed what’s typical or changes noticeably, it’s often a sign that something else is going on. This can show up as consistently needing to add water more than usual, seeing air in the return lines, or having trouble keeping the pump fully primed. In some cases, wet or soft areas may begin to appear around the pool or nearby yard. These types of patterns don’t always point to a visible issue, and leaks can develop gradually without obvious signs at first.
The Bucket Test (Initial Evaluation)
The bucket test is a simple way to compare evaporation with actual pool water loss.
It involves placing a bucket of water on the pool steps and comparing the water level inside the bucket to the pool over a 24-hour period. If the pool loses more water than the bucket, it strongly indicates that a pool leak is present.
For step-by-step instructions, see our guide on how to properly perform a pool bucket test.
Limitations of Basic Testing
While the bucket test can help indicate whether a leak may be present, it doesn’t provide enough detail to fully understand the problem. It won’t tell you where the leak is coming from, whether it’s related to the structure or the plumbing, if the issue is underground, or how severe it may be. Another helpful step is comparing water loss with the system running versus when it’s turned off, which can offer additional clues about where the issue may be originating. For more detail, see our guide on the pump on / pump off pool leak test.
Is Water Loss Normal When a Pool Is Covered?
A pool cover can significantly reduce evaporation, but finding a lower water level underneath a cover does not automatically mean the pool has a leak.
The first thing to determine is where the missing water is located. With some winter covers, rain and melted snow can collect on top of the cover. If water is pumped off the cover, pool water may also be removed if the cover is displaced, damaged, or sitting low enough to interact with the pool water beneath it.
Water loss beneath a covered pool becomes more suspicious when the pool level continues dropping significantly without an obvious explanation. A leak may be located in the liner, pool structure, fittings, light, skimmer, or underground plumbing system.
If the pool is open and operational, don’t try to judge a leak based on evaporation estimates alone.
Evaporation and Saltwater Pools
Saltwater pools do not evaporate at a different rate than traditional chlorine pools. Evaporation is determined by environmental conditions, not by the type of sanitizer used.
With a saltwater pool, it’s important to note that salt does not evaporate. This means, if your pool is evaporating, your salt levels should not drop (or any drop should be minimal). The only time salt leaves the pool is when water is lost, such as through:
- Leaks in the pool or pool plumbing system
- Splash-out from heavy use
- Backwashing or draining
Pro Tip
If your salt levels are consistently dropping without heavy splash-out or backwashing, it’s a strong indication that water is leaking from the pool and not evaporating. This is often an early sign of a pool leak.
Why Some Leaks Are Not Visible
Not all pool leaks show obvious signs, and many occur in places that aren’t visible during a standard check. Issues are often found in underground plumbing lines, hidden fittings, or connections that are sealed behind or beneath the pool structure. Because of this, these types of leaks cannot be identified through visual observation alone and may not create immediate surface symptoms. In many cases, they develop gradually and can worsen over time if not properly diagnosed. Learn more about how these issues occur in underground pool plumbing leaks.
Why Proper Testing Matters
Leaks that are not properly diagnosed the first time often lead to unnecessary repairs, guesswork, and additional costs. In many cases, homeowners hire a company that relies on visual inspection alone. When the leak is not found, a second company is then needed to perform proper testing, resulting in paying twice to identify the same problem.
Accurate testing from the start helps ensure the problem is correctly identified and prevents unnecessary work.
Professional Leak Detection
Professional leak detection involves a range of specialized diagnostic methods designed to accurately identify the source of water loss. This may include pressure testing of plumbing lines, isolating individual components of the system, using advanced listening equipment to locate underground or structural leaks, and performing dye testing where needed. By evaluating the pool system as a whole rather than relying on visual checks alone, this approach allows for precise identification of the problem so that any necessary repairs can be properly targeted.
When Further Testing Should Be Considered
Further evaluation may be appropriate when:
- Water loss exceeds normal evaporation ranges
- The bucket test suggests a leak
- The source of water loss is unclear
- Water must be added frequently
- Previous evaluations did not identify the issue
Early detection can help prevent more extensive damage and unnecessary repairs.
Loss & Evaporation
Many pools lose water due to evaporation. However, water loss that exceeds normal ranges may indicate a leak.
Saltwater pools do not evaporate faster than traditional pools, but changes in salt levels can provide additional insight into whether the pool is leaking.
Accurately determining the cause of water loss is essential before proceeding with repairs. If the cause of water loss is still unclear, further diagnostic testing may be required to accurately identify the source.
Frequently Asked Questions
How do I know if my pool is leaking or just evaporating?
The most reliable way to tell is by comparing water loss over time. Evaporation is gradual and consistent, while leaks often cause faster or irregular water loss. A bucket test can help indicate the difference, but professional testing is needed for confirmation.
How much water loss is normal in a pool?
Most pools lose about 1/8” to 1/4” of water per day due to evaporation. Factors like heat, sun exposure, and wind can increase this amount. Consistent water loss beyond this range may indicate a leak.
Does pool water evaporate under a cover?
Evaporation can still occur under a pool cover, but at a significantly reduced rate. If you are seeing noticeable water loss with a cover on, it may indicate a leak rather than evaporation.
Can evaporation cause my pool to lose inches of water?
Evaporation can cause noticeable water loss over time, especially in hot or windy conditions. However, losing several inches of water quickly or consistently is more likely due to a leak.
Will a pool leak always be visible?
No. Many leaks occur in underground plumbing or hidden areas of the pool system and may not show visible signs. This is why testing is often required to confirm the source of water loss.
Is the bucket test enough to confirm a pool leak?
The bucket test is a useful starting point, but it cannot determine the location or cause of a leak. It only indicates whether water loss may be greater than evaporation.
Do saltwater pools lose water differently than chlorine pools?
No. Evaporation rates are the same regardless of pool type. However, if salt levels are dropping along with water loss, it may indicate a leak rather than evaporation.
What should I do if I think my pool is leaking?
If water loss exceeds normal evaporation levels or continues over time, further testing should be performed. Professional leak detection can confirm whether a leak exists and identify the source.
Can a pool leak get worse over time?
Yes. Most leaks will worsen if left unaddressed. What starts as minor water loss can lead to larger plumbing or structural issues.
When should I have my pool tested for a leak?
You should consider testing if you are frequently adding water, noticing changes in water loss patterns, or if basic tests like the bucket test suggest a possible leak.
Not Sure If It’s a Leak or Evaporation? Do the Bucket Test
Instead of guessing how much water your pool should be losing, compare it against evaporation at your own pool.
Our bucket test takes 24 hours and gives you a much clearer answer. If the pool drops farther than the water inside the bucket, the additional water loss indicates that a leak may be present.
Follow Our Step-by-Step Pool Leak Bucket Test
If the test indicates a leak, review the common signs your pool has a leak or find information about professional pool leak detection in New Jersey.
