Why Is My Pool Losing Water?

Water loss is one of the most common concerns pool owners face. While some water loss is normal, consistent or excessive loss is often the first sign of a hidden problem — especially a pool leak.

Understanding the difference between normal evaporation and leak-related water loss can help you decide when it’s time to take action.

How Much Water Loss Is Normal?

All pools lose some water to evaporation.

Typical evaporation rates:

  • ¼ inch per day during hot, windy, or dry weather

  • Less during cooler or humid conditions

  • Slight increases with heavy pool use or water features

If your pool is losing more than ¼ inch per day, especially consistently, evaporation alone is unlikely to be the cause.

The Bucket Test: Evaporation or Leak?

A simple way to compare evaporation is the bucket test:

  1. Fill a bucket with pool water

  2. Set it on a pool step so water levels match

  3. Mark the water levels

  4. Wait 24 hours

If the pool level drops more than the bucket level, the pool is likely leaking.

Common Reasons Pools Lose Water

Evaporation and Splash-Out

Normal causes include:

  • Hot sun and wind

  • Heavy swimming activity

  • Water features or spillovers

  • Manual vacuuming or backwashing

These losses are predictable and occasional.

Underground Plumbing Leaks

One of the most common causes of ongoing water loss.

Signs include:

  • Water loss only when the pump is running

  • Air bubbles in returns

  • Pump losing prime

  • No visible leak inside the pool

These leaks occur beneath concrete or soil and often go unnoticed without testing.

Skimmer, Return, and Fitting Leaks

Pool penetrations are frequent leak points:

  • Skimmer throats

  • Return fittings

  • Light niches

  • Floor drain assemblies

Even small separations can result in steady water loss.

Cracks or Structural Issues

Concrete pools may develop:

  • Hairline cracks

  • Separation at plastic-to-plaster interfaces

  • Deterioration around fittings

Vinyl liner pools may experience:

  • Seam failures

  • Floor damage

  • Wall penetration leaks

Autofill Systems Masking Water Loss

Automatic water levelers can hide leaks by constantly refilling the pool.

Homeowners may notice:

  • Rising water bills

  • Chemical dilution

  • Salt levels dropping

  • No visible change in water level

Autofills are one of the most common reasons leaks go unnoticed for long periods.

Why Pools Sometimes Only Lose Water When Running

Many leaks are pressure-dependent.

When the system is on:

  • Pressure-side leaks push water out

  • Suction-side leaks pull air in

  • Underground cracks widen under flow

If water loss slows or stops when the system is off, plumbing leaks are likely.

Can Pool Equipment Cause Water Loss?

Yes. Common equipment-related causes include:

  • Leaking pump seals

  • Cracked filter tanks

  • Faulty multiport valves

  • Heater or salt cell leaks

Equipment leaks are often intermittent and may only appear during operation.

Why Ignoring Water Loss Gets Expensive

Unresolved water loss can lead to:

  • Higher water and utility bills

  • Excess chemical or salt usage

  • Soil erosion beneath decks

  • Settling or cracking concrete

  • Larger, more expensive repairs later

Early detection prevents long-term damage.

How Four States Leak Detection Finds the Cause

At Four States Leak Detection, we use professional diagnostic methods to locate leaks accurately, including:

  • Pressure testing of individual plumbing lines

  • Acoustic listening equipment

  • Dye testing of suspected areas

  • In-pool inspections without draining when possible

  • Non-destructive testing to avoid unnecessary excavation

We focus on finding the source, not guessing at repairs.

When to Call a Pool Leak Specialist

Schedule professional leak detection if:

  • Water loss exceeds normal evaporation

  • The pool loses water when running

  • Salt or chemicals need constant replacement

  • Autofill systems run frequently

  • Soft ground, settling, or cracks appear nearby

  • Previous repairs didn’t solve the problem

Pool Leak Detection in the Four States Region

Four States Leak Detection provides professional pool leak detection services across Missouri, Kansas, Oklahoma, and Arkansas. We work on vinyl liner, concrete, fiberglass, residential, commercial, and HOA pools.

Our approach is simple: accurate testing, clear explanations, and no unnecessary damage.