Concrete Pool Leak: The Usual Suspects (Cracks, Skimmers, Lines, and Lights)
Concrete pools can leak in a bunch of places, but the pattern is usually predictable. Start with stop-level behavior, then confirm with pump ON/OFF and the bucket test.
Schedule leak detection:
PoolLeakFix is an info + scheduling hub. Leak detection/repairs are performed by local pros.
Let's narrow it down: what's happening with your pool?
Pick the closest match. You'll get two quick checks, what it usually means, and the clean next step.
Choose the best match – you can always scroll back and pick another.
Quick answers (jump to your match)
Water loss with pump OFF
Use a simple overnight mark so you are not guessing.
- Quick check #1: Mark the waterline at night, keep the pump OFF, and re-check in the morning.
- Quick check #2: Run a 24-hour bucket test to compare pool drop vs bucket drop.
What it usually points to: A leak that does not require pump pressure (structure, fitting, or a line that can leak without runtime).
Next step: If the pool drops more than the bucket with the pump OFF, schedule detection so you stop chasing false causes.
Loss increases during pump runtime
Confirm the pattern before anyone touches decking.
- Quick check #1: Run pump for 2 hours, re-check; then pump OFF for 2 hours and compare.
- Quick check #2: If you have features (spa spillover/waterfall/cleaner), run them one at a time and watch if loss changes.
What it usually points to: Pressure-side plumbing or a feature line that leaks only when pressurized.
Next step: Once you confirm pump ON = faster loss, a pro can isolate the exact line with testing instead of guesswork.
Stops at the same level (the waterline clue)
Stop-level behavior is one of the strongest leak signals.
- Quick check #1: Let the water fall until it stops and note the exact level (tile line, light, skimmer, returns).
- Quick check #2: Dye-test fittings at that exact level with the pump OFF for a cleaner signal.
What it usually points to: A leak at or just below the stop level (skimmer throat, light niche, return fitting, crack).
Next step: Share the stop level when you schedule – it saves time and helps the pro start in the right zone.
Mushy ground / wet area near pool
Wet soil is a line-path clue, not just a nuisance.
- Quick check #1: Look for consistently wet soil, washed-out sand, or settling near the wet area.
- Quick check #2: Note whether the wet spot changes when the pump runs vs when it is off.
What it usually points to: An underground line leak or a leak under/near the deck pushing water outward.
Next step: If you see soil movement or settling, schedule detection early to prevent bigger deck damage.
Suction-side clues (air / prime issues)
Air issues can be a separate problem or part of the leak story.
- Quick check #1: Confirm water level is high enough for the skimmer; check the skimmer weir.
- Quick check #2: With pump running, lightly soap-test visible joints/valves at the pad for air pulling in.
What it usually points to: A suction-side air leak (lid O-ring, valve stem, union, skimmer line) – sometimes paired with water loss.
Next step: If you cannot stabilize prime or bubbles persist, a pro can isolate suction-side issues safely.
Cracks / tile line / structural suspicion
Structural leaks are fixable – but confirm the exact location first.
- Quick check #1: Inspect tile line/grout/cracks for staining, flaking, or a weeping line.
- Quick check #2: Dye-test suspected areas with pump OFF.
What it usually points to: Shell crack, tile/grout failure, or a fitting/collar leak near the surface.
Next step: Confirm category + location before anyone proposes cutting, resurfacing, or major work.
Unsure pattern (fast triage)
Answer one question and the troubleshooting lane becomes obvious.
- Quick check #1: Does it drop faster with pump ON? (Yes often points to pressure-side or pad.)
- Quick check #2: Does it stop at a specific level? (Yes is a huge clue.)
What it usually points to: You likely have enough signal to prioritize one test (bucket, stop level, pump ON/OFF).
Next step: If you cannot get a pattern, schedule detection and share what you have noticed – pros can still isolate it fast.
Concrete pools leak in predictable zones
Most concrete (gunite) leak cases land in the same zones: skimmer throat, light niche/conduit, returns, cracks, or underground lines. The fastest path is stop-level + pump ON/OFF + bucket test logic.
Cracks: do not assume every crack leaks
Some surface cracking is cosmetic. Use dye with pump OFF. If dye is pulled in consistently, you have a confirmed intake point.
Skimmer throats and light niches
These are high-probability leak points because they combine penetrations, joints, and materials that move differently over time.
Related Guides
- Pool Losing Water in Winter (Florida): Normal Evaporation or a Leak?
- Pool Leak Insurance: Is It Covered? What Policies Usually Pay For (and What They Don't)
- Pool Leak Repair Options: What "Fix" Actually Means (and What It Costs You in Time)
- Vinyl Liner Pool Leak: How to Find It (Without Losing Your Mind)
- Fiberglass Pool Leak: What's Different (and Where to Look First)
Schedule leak detection
Helpful clues: stop level (if any), whether loss increases while the pump runs, autofill present, heater use, and any air symptoms.
Concrete Pool Leak: The Usual Suspects (Cracks, Skimmers, Lines, and Lights) FAQs
What are the most common concrete pool leak points?
Skimmer throats, light niches, returns, cracks, and underground lines are common suspects.
Does every crack mean a leak?
No. Use dye with pump OFF to confirm consistent intake before treating it as a leak.
What does stop-level behavior tell me?
It often reveals the elevation of the leak so you can focus testing in the right zone.
If loss increases with pump runtime, what is likely?
Often pressure-side plumbing, feature lines, or equipment pad fittings under pressure.
What is the fastest way to confirm leak vs evaporation?
A 24-hour bucket test compares pool drop to a controlled reference in the same conditions.