Is Your Pool Losing Water? How to Tell If It's a Leak or Evaporation

Every pool owner in Houston has had the same thought at some point: "Is my pool losing too much water?" You fill it up on Monday, and by Friday the water line has dropped noticeably. You add water again, and the cycle repeats. Is it the Houston heat doing its thing, or is something actually wrong with your pool?

The truth is, every pool loses water to evaporation — especially in Houston's hot, windy climate. But there's a big difference between normal evaporation and an actual leak. A small pool leak can waste thousands of gallons of water per month, drive up your water bill, erode the soil around your pool, and eventually cause serious structural damage.

The good news is that you can figure out which one you're dealing with. Here's how to tell the difference between normal water loss and a pool leak, including a simple DIY test you can do this weekend, the warning signs that point to a real problem, and when it's time to call a professional.

Normal Evaporation Rates in Houston

Before you can identify abnormal water loss, you need to understand what's normal. Houston's climate creates some of the highest evaporation rates in the country, and those rates change significantly throughout the year.

During the peak of summer — June through September — a Houston pool can lose approximately ¼ inch of water per day, or roughly 1½ to 2 inches per week. That's a significant amount. For a standard 15,000-gallon residential pool, that works out to about 150 to 200 gallons per week in evaporation alone.

During the cooler months — November through February — evaporation slows to roughly ⅛ inch per day, or about ¾ to 1 inch per week. The reduced sunlight, lower temperatures, and shorter days all contribute to less water loss.

Several factors affect how quickly your specific pool evaporates:

• Sun exposure: A pool in full sun all day will evaporate faster than one with shade from trees or structures.
• Wind: Wind moving across the water surface accelerates evaporation dramatically. Houston's Gulf breezes and occasional strong winds can double the evaporation rate on a given day.
• Humidity: On those rare dry days in Houston, evaporation increases. When humidity is high (which is most of the time here), evaporation slows because the air is already saturated with moisture.
• Water features: Waterfalls, fountains, bubblers, and spillovers increase evaporation significantly because they expose more water surface area to air. A pool with an active waterfall can lose 50% more water to evaporation than a still pool.
• Pool temperature: Heated pools evaporate faster. If you run a heater or heat pump, expect higher water loss.

The Bucket Test: Your Best DIY Diagnostic

The bucket test is the simplest and most reliable way to determine whether your pool is losing water to evaporation or to a leak. It works by creating a controlled comparison: a bucket of pool water exposed to the exact same conditions as the pool itself. If the pool loses more water than the bucket, the excess loss is coming from something other than evaporation.

Here's exactly how to do it:

1. Get a 5-gallon bucket — a standard plastic bucket from any hardware store works fine. Make sure it's clean.
2. Fill the bucket about three-quarters full with pool water. Don't use tap water — you want the same temperature water so the evaporation rates match.
3. Place the bucket on the first or second step of your pool so that it's partially submerged in the pool water. Weigh it down with a rock or brick inside if needed to keep it stable. The bucket needs to sit in the pool so both water bodies experience the same temperature and wind conditions.
4. Mark the water level inside the bucket with a piece of tape or a waterproof marker. This is your control measurement.
5. Mark the pool water level on the outside of the bucket (or use a piece of tape on the pool wall at the water line). This is your pool measurement.
6. Turn off the auto-fill on your pool if you have one. You need to measure actual water loss, not compensated water loss.
7. Wait 24 hours. Do not swim in the pool during the test. Do not run water features, waterfalls, or the spa. Keep conditions as controlled as possible.
8. Compare the two levels after 24 hours. Measure how much the water inside the bucket dropped and how much the pool water dropped.

Interpreting the results:

• If the bucket water and pool water dropped by roughly the same amount, your water loss is likely due to evaporation. No leak.
• If the pool water dropped noticeably more than the bucket water — say ¼ inch or more difference — your pool is likely leaking.
• If the pool water dropped significantly more (½ inch+ beyond what the bucket lost), you almost certainly have a leak and should call a pool leak detection professional.

For the most accurate results, run the bucket test twice: once with the pump running and once with the pump off. If you lose more water with the pump running, the leak is likely in the plumbing (pressure side or suction side). If you lose the same amount either way, the leak is more likely in the pool shell itself.

Warning Signs That Point to a Real Leak

The bucket test is your best starting point, but there are other telltale signs that distinguish a leak from normal evaporation. If you notice any of the following, take them seriously:

Water Loss Exceeds the Bucket Test

This is the most definitive sign. If the bucket test confirms your pool is losing more water than evaporation accounts for, you have a leak somewhere in the system. Even a small leak — one that loses an extra ¼ inch per day beyond evaporation — can add up to over 7,000 gallons of wasted water per month in a standard residential pool.

Wet or Soggy Spots Around Pool Equipment

Check the area around your pool pump, filter, heater, and plumbing connections. Persistent wet spots, puddles, or muddy soil around the equipment pad often indicate a leak in the above-ground plumbing. Look for drips at unions, valves, fittings, and where pipes connect to the equipment. Also check the backwash line and waste line for unexplained water flow.

Cracks in the Pool Shell

Visible cracks in the plaster, pebble finish, fiberglass, or gunite surface of your pool are common leak sources. Even hairline cracks can allow water to seep through, especially if they extend through the structural shell. Pay particular attention to the areas around fittings, returns, the main drain, and the skimmer throat — these are stress points where cracks tend to develop first.

Air Bubbles Coming from Return Jets

If you see a steady stream of small air bubbles pushing out of your return jets when the pump is running, air is getting into the suction side of the plumbing. This usually means a crack or loose fitting on the suction line between the skimmer and the pump — and where air gets in, water gets out. This is one of the most commonly overlooked signs of a plumbing leak.

Algae Growth Despite Proper Chemical Balance

A pool that's constantly losing water is also constantly losing the chemicals dissolved in that water. If you find yourself adding chlorine and other chemicals more frequently than usual, and algae keeps coming back even though your chemistry is balanced, a leak could be the culprit. The continuous introduction of fresh, untreated water dilutes your chemicals and creates an environment where algae thrives.

Settling or Shifting Pool Deck

Water leaking from a pool erodes and saturates the surrounding soil over time. In Houston's clay soil, this is especially problematic. You may notice the pool deck settling unevenly, cracks appearing in the concrete or pavers, or a gap developing between the coping and the deck. These are signs of soil erosion caused by a persistent leak underneath the deck or from the pool shell.

Common Pool Leak Locations

Pool leaks can occur anywhere in the system, but some locations are far more common than others. Understanding where leaks typically happen can help you communicate with your leak detection professional and understand the diagnosis:

• Shell cracks: Cracks in the pool's plaster, pebble, or fiberglass surface. These can develop from ground movement, age, freeze-thaw cycles, or improper construction.
• Underground plumbing lines: The pipes that run between the pool and the equipment pad are buried underground and can crack, separate at joints, or develop holes from root intrusion or soil movement.
• Fittings and returns: The connection points where plumbing meets the pool wall — return jets, suction lines, and the main drain fitting — are common failure points. The seal between the fitting and the pool shell can deteriorate over time.
• Skimmer: The skimmer is one of the most common leak locations. Cracks can develop in the skimmer throat, at the base where it connects to the pool wall, or in the plumbing connection behind the skimmer. The joint between the skimmer and the pool shell is a known weak point.
• Light niche: The conduit that runs from the pool light to the junction box can act as a pathway for water to escape. Cracks around the light niche or a deteriorated conduit seal are frequent leak sources that are easy to overlook.
• Tile line: If the bond beam (the structural top edge of the pool) has cracks behind the tile, water can seep through the tile line. This is common in older pools where the coping or tile adhesive has deteriorated.

When DIY Isn't Enough: Calling a Professional

The bucket test and visual inspections can tell you that a leak exists, but they usually can't tell you exactly where it is. Finding the precise location of a pool leak requires specialized equipment and expertise — especially when the leak is underground, inside the pool shell below the waterline, or in buried plumbing.

It's time to call a professional pool leak detection company when:

• The bucket test confirms abnormal water loss but you can't find an obvious source
• You've fixed visible issues (loose fittings, cracked returns) but the water loss continues
• The pool is losing more than ½ inch per day beyond normal evaporation
• You see signs of underground leaks — soggy soil, settling deck, or unexplained wet areas around the pool
• You suspect a plumbing leak but can't access the buried pipes

How Professional Pool Leak Detection Works

Professional pool leak detection uses specialized technology to pinpoint leaks without unnecessary demolition or guesswork. At Exact Leak Detection HTX, our pool leak detection service uses a combination of methods depending on where we suspect the leak:

• Pressure testing: We isolate and pressurize individual plumbing lines to determine whether each line holds pressure or is losing it. This quickly identifies which pipe — if any — has a breach.
• Hydrophone listening: A specialized underwater microphone detects the sound of water escaping through cracks or holes in the pool shell. By moving the hydrophone systematically along the pool floor, walls, and fittings, we can identify the exact location where water is escaping.
• Dye testing: Once we've narrowed down a suspected area, we use specially formulated dye near the crack, fitting, or joint. If water is flowing out, the dye is visibly pulled toward and into the leak point, confirming the exact location.
• Thermal imaging: For leaks that are affecting the surrounding soil or deck, thermal cameras can detect temperature differences caused by water saturation — revealing the leak's path and impact area.

Every inspection includes a detailed report documenting what we found, where the leak is located, and what type of repair is recommended. This gives you — and your pool contractor — a clear roadmap for fixing the problem without unnecessary digging or guesswork.