The Top 2 Reasons Your Pool Is Losing Water, According to Experts

It’s normal for pools to lose about ¼ inch of water each day from splashing or evaporation. Significant water loss may be due to either excessive evaporation or a leak. Pool owners can determine whether evaporation or a leak is causing their pool to lose water by using the bucket test and the dye test. Evaporation issues can be solved by installing a solar cover. Pool leaks typically need to be addressed by pool repair professionals.

I’ve seen firsthand how a little water loss can make you worry, especially when you’re trying to enjoy a sunny day by the pool. To add some context, that ¼ inch daily loss translates to roughly 150-200 gallons per month for an average-sized pool, depending on its surface area. Evaporation is a natural process driven by heat, wind, and low humidity, which can pull water molecules from the surface faster than you’d expect. A solar cover, as mentioned, is a game-changer—it can reduce evaporation by up to 85%, according to studies from the Department of Energy. If you’re in a hot climate like I am, this can save you hundreds of gallons a month, not to mention keeping your pool warmer. For leaks, though, don’t try to DIY everything. I once thought I could patch a small crack myself, only to realize it was a symptom of a bigger plumbing issue. Calling a pro early can save you a headache.

Q: Why Is My Pool Losing Water, and How Can I Fix It?

Nothing can ruin a relaxing day of lounging poolside or kicking back on a pool float like the realization that your pool is rapidly losing water. All pools lose a small amount of water each day to evaporation and splashing. However, an excessive drop in a pool’s water level is typically due to either a more significant evaporation issue or a leak. Both causes require attention, as low water levels can lead to more serious problems, such as poor pool circulation.

If there’s not enough water in a pool, the pump and filtration systems’ efficiency becomes compromised. As a result, the pool’s water can become cloudy, algae growth can increase, and the pool equipment may even become damaged. Consistent water loss also means frequent pool refilling, which increases water usage and utility bills and requires more chemicals to maintain water quality and hygiene. If water loss is happening because of a leak, the rapid and excessive water loss can threaten the pool’s structure and surrounding materials. That’s why it’s so important for homeowners to be able to spot the difference between evaporation and water leaks in their pools.

Let me tell you, a cloudy pool from low water levels is no fun to deal with—been there! Beyond the aesthetic issues, poor circulation can strain your pump, potentially shortening its lifespan by months or even years. A study by the Pool & Hot Tub Alliance suggests that running a pump with insufficient water can increase energy costs by 10-15% due to inefficiency. For leaks, the structural risks are real. I’ve seen neighbors ignore small leaks, only to end up with cracked concrete or eroded soil that cost thousands to fix. A quick tip: keep an eye on your water bill. A sudden spike, especially in summer, might not just be from refilling but could hint at a hidden leak. Regular checks can catch these issues before they turn into a wallet-draining disaster.

How Much Pool Water Loss Is Normal?

According to Alicia Toedter, senior manager of content strategy at the national pool and spa care brand Leslie’s, “The average pool loses about ¼ inch of water per day unless a solar pool cover is used to cut down on evaporative water losses.” Evaporation is the primary cause of this water loss, and climate and environmental factors can exacerbate it.

“Pools in especially hot, dry, or windy climates can lose even more, as these factors increase the evaporation rate,” says Toedter. “Other things like splash-out and backwashing the filter can also remove water from the pool.”

These causes of water loss are normal, so it’s important to monitor water levels regularly to get to know typical reduction changes versus potential leaks. As a rule, it’s generally only necessary to add 1 to 2 inches of water to the pool each week. “If you’re noticing the water level dropping more than a couple of inches per week for no apparent reason, odds are you’re dealing with a pool leak,” Toedter adds.

In my experience, keeping a log of your pool’s water levels weekly can really help you spot patterns. For instance, in dry, windy areas like Arizona, you might lose closer to ½ inch per day without a cover—double the average! Data from the National Swimming Pool Foundation shows that uncovered pools in arid regions can lose up to 25% more water than those in humid climates. Splash-out is another sneaky culprit, especially if you’ve got kids cannonballing all day. A practical trick I’ve used is setting a reminder to check levels every Sunday; it’s a small habit that helps you catch issues early. If you’re adding more than a couple of inches weekly, don’t wait—start investigating for leaks to avoid bigger problems.

How to Identify Pool Water Evaporation vs. Leaks

An excessive drop in pool water levels (beyond expected splash and evaporation loss) often points to a leaky pool. To maintain pool health, homeowners need to know the difference between environmental conditions causing evaporation and structural damage or a plumbing issue causing leaks.

Pool water evaporates more quickly in the spring and summer—if the problem worsens with warmer weather, evaporation is the likely cause.

Pool evaporation rates increase in the warmer months of spring and summer when temperatures are consistently warm. Both higher temperatures and intense sunlight contribute to faster evaporation of water from a pool’s surface. If the water level in a pool drops more noticeably as the weather warms, it is likely that evaporation is the primary cause of water loss during these seasons. Additional environmental factors like lower humidity and increased wind can further accelerate this evaporation process. Rafi Friedman, president of Florida-based pool building company Coastal Luxury Outdoors, advises that pool owners pay regular attention to their pool and the weather forecast.

“Humidity levels play a big role in how quickly water will evaporate,” he says. “If things have been dry, more evaporation should be expected. If you notice a larger-than-usual dip in water level even when it’s humid, or especially if you’ve kept your pool covered, you may have a leak on your hands.”

Seasonal Water Loss Chart

If homeowners find themselves adding water to their pool at higher volumes or more frequently than average water loss rates require, this could be a sign of a leak. The best way to combat this issue typically involves installing a solar cover for the pool. Additionally, covering the pool area with a pool enclosure can also help. A pool screen enclosure costs between $5,708 and $16,608 on average.

I’ve noticed that evaporation can really sneak up on you in summer—those warm nights and sunny days just suck the water right out! The chart above is super helpful, but keep in mind these numbers assume an average 15,000-gallon pool. If your pool is larger, expect higher losses. For example, a 20,000-gallon pool might lose over 3,000 gallons in summer without a cover. A solar cover isn’t just about saving water; it can cut your heating costs by 10-20%, per energy studies, which is a nice bonus. I also recommend checking your local weather app for humidity levels. Low humidity days can double evaporation rates, so if your pool’s losing water even with a cover, it’s time to suspect a leak and run some tests.

Excessive moisture or an accumulation of standing water surrounding the pool is a clear sign that the pool is leaking.

When a pool leaks, the water typically seeps into the ground surrounding the pool. Depending on the pool’s location, this could result in sinking decks or patios, muddy or soggy spots in the grass, or even cracks appearing on the surface of the concrete surrounding the pool. “If you notice unusually soggy spots in your lawn, or water trickling out of your lawn into a nearby gutter or storm drain, it may be coming from your pool,” Friedman says. Over time, water seepage from a leaking pool can cause soil erosion or damage the pool’s structural integrity and the surrounding area. It’s important to address any signs of pool leaks right away to avoid costly repairs.

Soggy spots around the pool are a dead giveaway something’s wrong. I once noticed my patio tiles starting to shift, and sure enough, there was a small leak in the pool’s return line. Soil erosion from leaks can be a nightmare—studies show that prolonged water seepage can reduce soil stability by up to 30%, which might lead to costly foundation repairs. A quick trick is to walk around your pool after a dry spell; if you spot wet patches or sinking ground, don’t ignore it. Catching these early can save you from spending thousands on landscaping or structural fixes. If you’re unsure, a soil moisture meter (about $15 online) can help confirm if the ground’s wetter than it should be.

You may notice an increase in the amount of chemicals the pool requires as a water leak advances.

Treating a pool with chemicals is an essential part of both in-ground and above-ground pool maintenance. Homeowners may notice they need to increase the amount of pool stabilizers and other chemicals required to maintain the water quality if they have a swimming pool leak. The fresh water added from the hose to compensate for the leaked water will dilute the existing chemical balance in the pool, making it less effective. More chlorine, algaecides, and pH balancers are needed to keep the pool water clear and safe for swimming. “A sudden increase in chemical usage or difficulty maintaining proper water chemistry can…be indicators of a leak,” said Toedter. “This is especially true if you’re using an auto-fill valve that adds fresh water automatically.” Early leak detection in swimming pools can lessen pool maintenance costs in the form of water and chemicals.

I’ve been burned by this one before—my chemical costs spiked, and I couldn’t figure out why my pool kept looking off. Turns out, a small leak was diluting everything. The Pool & Hot Tub Alliance notes that a leak can increase chemical usage by 20-30% because fresh water lacks the balanced chemistry of treated pool water. A practical tip: test your water chemistry weekly with a good test kit (I like the ones with digital readouts for accuracy). If you’re adding way more chlorine or stabilizer than usual, especially with an auto-fill system, it’s a red flag. Catching this early can save you from spending an extra $50-100 a month on chemicals.

For those with automatically filling pools, soaring water bills are another sign of a pool leak.

Automatic filling pools are designed to maintain water levels seamlessly; however, a leak will cause the system to go into overdrive. More water will be needed than usual, which will result in significantly higher water costs over time. Since the pool is being refilled constantly, it may not be obvious that the pool is losing water until the utility bill comes. If a homeowner notices the system is running more frequently than normal—especially without increased usage or evaporation conditions—it’s likely a sign that water is escaping through an unseen leak.

Man, those water bills can hit you like a ton of bricks! I once got a bill that was double my usual amount, and it was because my auto-fill was masking a leak. According to the EPA, a pool leak losing just 1/8 inch per day can add up to 1,000 gallons a month—enough to spike your bill by $10-20 depending on local rates. A simple trick I use is to listen for the auto-fill valve; if it’s kicking on more than once or twice a day, something’s up. Check your water meter before and after a 24-hour period with the pool pump off to confirm if extra water’s being used. It’s a quick way to catch a leak before your wallet takes a hit.

Visible cracks in the lining or surface of the pool can signal a leak and may lead to larger structural issues.

It’s worth doing a visual inspection of the pool for any cracks. If there is water seeping through these fractures, it can undermine the integrity of the surrounding area and the base of the pool. “Once you’ve found the crack, drain your pool below that point, then address the problem,” says Friedman. “Small cracks can be dealt with using at-home patch kits or sealer, while bigger ones should be left to professionals.” Taking a proactive approach to pool leak detection will prevent escalated repair costs and a possible pool closure to fix a significant leak.

Cracks are no joke—I ignored a hairline crack once, thinking it was cosmetic, and ended up with a much bigger repair bill later. Small cracks might seem fixable with a $20 patch kit, but if they’re wider than 1/8 inch or keep growing, you’re better off calling a pro. The American Concrete Institute says untreated cracks can expand by 10-15% annually under water pressure, risking major structural damage. A good habit is to inspect your pool’s surface monthly, especially around fittings and lights, where cracks often start. If you spot one, mark it with a pencil and check if it grows over a week. That’ll help you decide if it’s a quick fix or time to call in the experts.

A “Bucket Test” Can Be Done to Determine Whether the Water Loss Is Due to a Leak or Excessive Evaporation

Jimmie Meece, brand president of national pool service franchise America’s Swimming Pool Company, recommends performing the “bucket test” to rule out normal evaporation and potentially detect a leak in a pool. To do this, fill a bucket with pool water and place it on the first or second step inside the pool so the water level inside the bucket matches the water level inside the pool. Mark both water levels inside and outside the bucket. Leave the bucket in this spot for 24 hours without adding any additional water to the pool during this time. Then, compare the water levels after the test window. “If the pool water, which is the outside mark on the bucket, goes down more than the inside water level, there is probably a leak,” says Meece. “Document the water level drop in inches.”

Meece also notes that if it rains during the 24-hour period, homeowners will need to repeat the bucket test to confirm the leak. As a follow-up test for a suspected leak, Meece also recommends the “24 hours on” test to differentiate between a leak in the plumbing system and one in the shell of the pool. To do this, fill the pool so the water level is neither above nor below the skimmer, then mark the level. Turn off any auto-fill valves and run the pool pump for a full 24 hours before checking the water level again. If the water level has dropped below the mark, it could indicate a plumbing leak. Meece adds that it’s important to make sure that no water is leaking from the “backwash line,” (the pipe carrying waste water away from the pool) when the pump is running. “If you’re losing water from the backwash line, you’ll need to repair or replace the multiport valve on your filter,” says Meece.

The bucket test is honestly one of the easiest ways to figure out what’s going on with your pool. I tried it last summer when I suspected a leak, and it was eye-opening how clear the results were. One thing to keep in mind: make sure the bucket is stable and won’t tip over—use a heavy one if possible. The Pool & Hot Tub Alliance suggests repeating the test over two days for accuracy, especially if weather conditions fluctuate. For the “24 hours on” test, I found it helpful to check the backwash line by feeling for dampness around the valve area. If you’re losing more than ½ inch in the pool compared to the bucket, don’t wait—start looking for that leak. It’s a simple test that can save you from bigger headaches down the road.

If You Do Have a Leak, a “Dye Test” Can Help You Pinpoint Its Location

Once it’s clear that the problem is actually a leak, it’s time to learn how to find a leak in a pool. “Certain clues may help you pinpoint exactly where the leak is coming from, if not readily apparent,” Toedter says. “For example, does the water level drop faster when the pump is on? If you turn the pump off and let the water level drop, does it stop at a certain point in the pool?” The most common leak areas include the skimmer, pool lights, plumbing returns, cracks or tears in pool surfaces, and plumbing joints and unions that connect your equipment to the pool.

In the absence of these clues, a dye test can help determine the leak location. This is when a small amount of dye—food coloring or a specially formulated dye—is introduced to the pool while the water is still and the pumps are not running. Apply the dye near cracks, fittings, and around the edges of the pool liner—anywhere leaks are most likely to occur. The dye will flow toward the leak to visually show the homeowner where the pool is losing water and make the process of finding a pool leak much easier. Once identified, some cracks can be temporarily repaired with a pool patch, but it’s a good idea to have a professional inspect the pool and perform more permanent repairs.

The dye test is like detective work for your pool—it’s actually kind of fun! I used food coloring once and watched it get sucked right into a tiny crack near the skimmer. Pro tip: use a syringe or dropper for precision, and only a few drops, so you don’t stain the pool. According to pool industry reports, about 50% of leaks occur around fittings like skimmers or lights, so start there. If the water level stabilizes at a certain point when the pump’s off, that’s a clue the leak’s at that level—saved me hours of searching once. For temporary patches, I’ve had decent luck with underwater sealants, but they’re just a Band-Aid. A pro can fix it right and check for other weak spots you might miss.

Who to Call for Pool Leak Repair

For advanced leak detection, Toedter says that a pool service professional may be needed to pinpoint the exact location. “This is especially true for underground plumbing leaks that may have resulted from freeze damage or shifting soil,” she adds. A pool repair company has the expertise and tools for detecting pool leaks that might not be readily accessible to homeowners. Some of the best pool cleaning services and best pool installation companies also offer repairs, so homeowners who already use these services may want to inquire about this if they suspect a leak.

First, the pool technician will perform a pool inspection to assess the problem. A pool inspection costs about $125 to $250. Following a thorough inspection, a pool service specialist may recommend solutions ranging from pool resurfacing or liner replacement (homeowners can expect pool resurfacing costs of around $6,500, and pool liner replacement costs $2,393 on average). The cost of pool leak repairs seems minimal when the root cause of water loss is identified and effectively addressed. Additionally, pool professionals often provide valuable maintenance tips and strategies to prevent future issues and keep the pool in optimal condition for safe and enjoyable use.

Calling a pro is worth every penny when you’re dealing with tricky leaks. I once tried to hunt down an underground plumbing leak myself and wasted days—turns out, it was a tiny pipe joint issue only a pressure test could find. The Pool & Spa News reports that professional leak detection can save up to 70% on repair costs by catching issues before they escalate. If you’re budgeting, factor in that inspections are usually $150-200 in my area, but they can pinpoint leaks with tools like acoustic sensors that we just don’t have at home. Ask your technician for maintenance tips, too—I got some great advice on winterizing my pool to prevent freeze damage, which has saved me from future leaks.