How to fix leaks in an inground pool

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Introduction

Losing water faster than normal in your inground pool? Even a small leak can lead to big problems over time—wasting water, raising utility bills, and damaging the surrounding structure. In this complete step-by-step guide, you’ll learn how to fix leaks in an inground pool, from pinpointing the source to sealing it properly. Whether it’s the liner, plumbing, or skimmer, we’ve got you covered.

Why Fixing Pool Leaks Matters

A leak in an inground pool doesn’t just cost you water—it can also cause serious structural issues if left unchecked. Common consequences include:

  • Soil erosion around the pool shell
  • Cracked decks and shifting tiles
  • Increased water and chemical costs
  • Pump and filter system strain
  • Damage to pool equipment and landscaping

Fixing leaks early helps maintain water balance, saves money, and preserves the integrity of your entire pool setup.

Step-by-Step Guide to Fixing Leaks in an Inground Pool

Step 1: Confirm You Have a Leak

Some water loss is normal due to evaporation, but here’s how to know if it’s a leak:

  • Bucket Test: Fill a bucket with pool water, place it on the step, and mark the water levels inside and outside the bucket. Wait 24 hours. If the pool water drops more than the bucket, you likely have a leak.
  • Check for Wet Spots: Walk around your pool and check for soggy ground, standing water, or unusual wet patches in the lawn.

Tip: Also check if the water loss only happens when the pump is running—it may point to plumbing leaks.

Step 2: Identify the Type and Location of the Leak

Common inground pool leak locations include:

  • Vinyl liner tears or punctures
  • Cracks in concrete or gunite pools
  • Around skimmers, lights, or returns
  • Main drain at the bottom of the pool
  • Underground plumbing lines

Use these strategies to help locate it:

  • Dye Test: With the pump off and water still, squeeze pool dye (or food coloring) near suspected leak points. Watch for dye being pulled into cracks or holes.
  • Check equipment pad: Look for water near your pump, filter, heater, and pipes.
  • Pressure testing: For plumbing leaks, consider hiring a pro to perform a pressure test on your lines.

Step 3: Patch a Liner Leak (Vinyl Pools)

For vinyl liner pools, small holes or tears can often be patched underwater using a vinyl patch kit.

To repair:

  1. Clean the area around the hole with a soft cloth.
  2. Cut a patch with rounded edges, about 1–2 inches larger than the hole.
  3. Apply underwater vinyl adhesive to the patch.
  4. Fold the patch and unfold it underwater near the leak.
  5. Press firmly for 30–60 seconds until it bonds.

Pro Tip: For above-water patches, drain the water below the hole and apply the patch dry for a stronger hold.

Step 4: Seal Cracks in Concrete or Gunite Pools

Concrete pools can develop surface cracks over time that leak water.

To repair minor cracks:

  1. Drain the water below the cracked area.
  2. Clean the surface with a wire brush.
  3. Use pool-grade hydraulic cement or epoxy sealant.
  4. Force the product into the crack using a putty knife or trowel.
  5. Smooth the surface and allow to cure as directed.

Tip: Hydraulic cement expands as it sets, making it ideal for sealing active leaks.

For large or structural cracks, consult a pool repair professional.

Step 5: Fix Leaks Around Skimmers, Returns, and Lights

Plastic skimmer boxes and fittings are common leak sources due to age or shifting.

To repair:

  • Skimmer throat leaks: Apply pool putty or silicone sealant around the joint where the skimmer meets the pool wall.
  • Return fitting leaks: Remove the fitting, apply Teflon tape or thread sealant, and reinstall.
  • Light conduit leaks: Use flexible sealant (like Butyl tape or epoxy putty) inside the conduit.

Caution: Always turn off electricity to pool lights before inspecting or sealing around them.

Step 6: Repair or Replace Leaking Plumbing Lines

If you suspect an underground leak:

  • Call a leak detection specialist to perform pressure tests or electronic leak detection.
  • If confirmed, the damaged section of PVC pipe may need to be dug up and replaced.
  • Use PVC primer and cement to install new fittings and test for leaks before backfilling.

Warning: Underground plumbing leaks are best left to professionals unless you have excavation experience.

Step 7: Monitor and Retest

After completing the repair:

  1. Refill the pool to its normal level.
  2. Re-do the bucket test or mark the water level with tape and observe for 24–48 hours.
  3. Watch for signs of recurring leaks (dye movement, air in pump, low pressure).
  4. Check equipment pad for moisture.

Tip: Keep a log of your water level checks to track any slow leaks.

Common Mistakes to Avoid

  1. Assuming All Water Loss Is a Leak
    • Evaporation can cause 1/4 to 1/2 inch per day.
    • Solution: Do a bucket test first to confirm.
  2. Skipping Surface Cleaning Before Patching
    • Adhesives won’t stick to dirty or rough surfaces.
    • Solution: Always clean and prep the area first.
  3. Using Household Sealants
    • Regular caulk or glue won’t hold up underwater.
    • Solution: Use pool-rated underwater adhesives only.
  4. Overlooking Equipment Leaks
    • Pumps, filters, and valves can leak just as easily.
    • Solution: Regularly inspect the equipment pad.
  5. Waiting Too Long to Act
    • A small leak today can become a major repair tomorrow.
    • Solution: Fix leaks as soon as you spot them.

Extra Tips & Pool Hacks

  • Add a pool leak detection kit to your maintenance supplies—great for finding slow or small leaks.
  • Track water bills monthly—a sudden spike can point to a hidden leak.
  • Use a leak-proof skimmer extension to reduce movement that causes cracks.
  • Install a pool liner pad to protect vinyl liners from punctures below.

🧰 Need more repair tips? Check out our article on how to install a new pool liner to keep your vinyl pool watertight and beautiful.

Conclusion

Learning how to fix leaks in an inground pool gives you the power to protect your investment, reduce water waste, and keep your backyard oasis running smoothly. Whether it’s a DIY patch on a vinyl liner or a call to a leak detection pro, the key is early detection and action. Stay alert, follow the steps, and your pool will stay leak-free and ready for summer fun.

💡 Final Tip: Set a reminder to check your water level weekly—early leak detection is always cheaper than major repairs.