Step 1: Confirm That the Pool Is Actually Losing Water

Swimming pools naturally lose some water through evaporation, splashing, backwashing, wind, and swimmer activity. Before diagnosing an underground plumbing leak, the first step is to determine whether the water loss appears abnormal.

A basic bucket test may help compare pool water loss with normal evaporation.

1. Fill a bucket with pool water.
2. Place the bucket on a pool step so it remains stable.
3. Mark the water level inside the bucket.
4. Mark the pool water level outside the bucket.
5. Operate the pool normally for a set period.
6. Compare the water-level changes.

If the pool drops noticeably more than the water inside the bucket, the pool may have abnormal water loss.

Step 2: Inspect the Pool and Equipment

The next step is a thorough visual inspection of the visible pool system.

Areas that should be checked may include:

• Pool pumps
• Filters
• Heaters
• Chlorinators
• Valves and unions
• Pump seals and drain plugs
• Visible pipes and fittings
• Skimmers
• Return fittings
• Pool lights and niches
• Main drains
• Tile lines
• Expansion joints
• Cracks in plaster or the pool shell
• Wet soil near the equipment pad
• Settling or erosion near the pool deck

A visible equipment leak may only occur while the pump is operating. Other leaks may occur when the system is off. Observing the pool under different operating conditions can provide useful evidence.

Step 3: Determine Whether Water Loss Changes With the Pump

Comparing water loss while the pool equipment is running and while it is off may help narrow down the type of leak.

These observations help guide the investigation, but they do not replace proper isolation and pressure testing.

Step 4: Dye Test Suspected Pool Openings

Dye testing may help identify water movement near suspected cracks, skimmers, return fittings, light niches, main drains, tile joints, or other pool penetrations.

The water should be calm during the test. A small amount of dye is released close to the suspected area. If the dye is drawn directly into an opening, that may indicate active water movement.

Dye testing is useful for shell and fitting leaks, but it does not fully evaluate underground plumbing lines.

Step 5: Isolate the Pool Plumbing Lines

If the visual and dye inspections do not identify the source, the pool plumbing may need to be isolated.

Individual plumbing branches may include:

• Skimmer suction lines
• Main drain lines
• Return lines
• Cleaner lines
• Spa suction lines
• Spa return lines
• Waterfall or water-feature lines
• Dedicated circulation lines

Isolation allows each section to be evaluated separately instead of testing the entire pool system as one large group.

Step 6: Pressure Test Each Pool Plumbing Line

Pressure testing is used to determine whether an isolated plumbing line can hold controlled pressure.

A properly isolated line is filled and tested under conditions appropriate for the pipe and system. The pressure is then observed for a period of time.

The results may show:

• The line holds pressure
• The line slowly loses pressure
• The line loses pressure quickly
• The test cannot be completed because isolation is incomplete
• A valve, fitting, plug, or accessible connection is leaking

A line that loses pressure may contain a leak, but the pressure test usually identifies the affected line rather than the exact underground repair spot.

Step 7: Locate the Suspected Underground Leak

Once a specific plumbing line is identified as leaking, additional methods may be used to narrow down the suspected location.

Depending on site conditions, the process may involve:

• Acoustic listening equipment
• Air and water testing
• Tracer-gas methods
• Electronic locating
• Reviewing the probable pipe route
• Listening near deck joints and penetrations
• Checking for wet or eroded soil
• Comparing deck movement with the suspected line path
• Selective exploratory access when necessary

Underground pool plumbing may run beneath concrete, landscaping, retaining walls, outdoor kitchens, patios, decks, or other improvements. The repair location should be based on evidence rather than convenience.

Step 8: Have a Master Plumber Interpret the Results

Leak-detection equipment provides information. It does not replace professional judgment.

Steven Shipler is a Texas Licensed Master Plumber and Responsible Master Plumber, Texas License #45825. That experience matters when interpreting pool pressure-testing results and recommending a repair.

A Master Plumber understands:

• Pressure and flow
• Pipe materials
• Valves and fittings
• Plumbing isolation
• Testing procedures
• Underground pipe routing
• Repair methods
• Excavation concerns
• Connections between pool and property plumbing
• Whether a proposed repair matches the evidence

Common Pool Leak Findings

Why Pool Leaks Are Common in Plano, Allen and Collin County

North Texas swimming pools are exposed to heat, drought, heavy rain, expansive clay soil, soil movement, and foundation or deck settlement. These conditions can place stress on underground pipes, pool shells, fittings, equipment connections, and surrounding concrete.

Pool leak problems in Collin County may involve:

• Soil expansion and contraction
• Deck movement
• Pool-shell cracking
• Shifted underground fittings
• Broken PVC pool plumbing
• Leaks near skimmers or returns
• Equipment deterioration
• Previous repairs that did not address the actual source

The city may change from Plano to Allen, McKinney, Frisco, Murphy, Lucas, Fairview, Wylie, or another Collin County community. The basic rule remains the same: test before excavating.

Mistakes to Avoid When Searching for a Pool Leak

• Assuming every water loss problem is evaporation
• Replacing the pump without testing the plumbing
• Breaking concrete based only on a wet area
• Testing multiple lines together without proper isolation
• Using excessive test pressure
• Ignoring leaks that only occur while equipment runs
• Assuming a failed line identifies the exact repair location
• Repairing a visible crack without confirming whether another leak exists
• Hiring someone who cannot explain the test results
• Approving major work without written findings

What a Professional Pool Leak Evaluation Should Tell You

At the end of a professional pool leak investigation, the property owner should understand:

• Whether abnormal water loss was confirmed
• Which parts of the pool were visually inspected
• Which lines were isolated
• Which lines held pressure
• Which lines lost pressure
• Whether the likely issue is structural, equipment-related, or plumbing-related
• The approximate suspected leak area
• Whether additional locating is recommended
• Whether concrete or excavation may be required
• Which repair option best matches the evidence

Frequently Asked Questions