# How to Find a Leak in a Pond in 2 Steps (and Choose the Right Repair)

Canonical URL: https://pondacademy.com/how-to-find-a-leak-in-a-pond
Author: Tory Jon
Published: 2019-06-26T08:00:00-05:00
Updated: 2026-09-21T16:05:11.645Z

Watching your pond level drop faster than expected is frustrating, especially when pond fish and equipment depend on a safe water level. Before assuming the liner has a hole, it helps to separate normal evaporation and edge overspill from a true leak.

Start with the preliminary tub comparison below to check whether the pond is losing more water than evaporation alone. If it is, use the two leak-location steps to narrow the source. Then choose a repair that matches the pond's construction.

## Is My Pond Leaking?

Ponds naturally lose water through evaporation. Weather and the amount of exposed water affect the rate, as explained in [FAO guidance on pond evaporation](https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6705e/x6705e02.htm#21a). A waterfall or stream can add splash loss, so there is no single weekly amount that is normal for every pond.

A container comparison can roughly screen for evaporation, but it cannot rule out a leak. [Pond specialist Demi Fortuna's evaporation method](https://www.pondtrademag.com/the-w-e-t-s-method-for-diagnosing-water-loss/) uses a broad tub near the water feature, with similar exposure and water temperature. Adapt it cautiously:

1. Turn off the auto-fill and mark the pond level.
2. Secure a broad, clean tub on level ground beside the pond, away from children and pets. Fill it to the rim so the sides do not shelter the water from sun or wind. Let overflow settle before marking its level.
3. Compare the tub and pond over the same rain-free period, ideally two days, while the pond operates normally. Mark and measure the vertical drop in each.
4. Restart after rain or refilling. If water temperatures or exposure differ substantially, the comparison is unreliable.

Fortuna also matches water movement when testing moving features. A still tub beside a waterfall cannot reproduce that evaporation or splash loss, so use the result only to decide whether closer inspection is worthwhile.

If the pond drops noticeably farther than the container, continue with the checks below. The extra loss could come from a leak, overspill, or splash outside the liner. Similar drops do not prove the pond is leak-free.

## How to Find a Pond Leak

Start with the easiest exterior checks. They may reveal a low edge or escaping waterfall before you need to shut down equipment.

### Step 1: Inspect the Edges for Overspill

A puncture is possible even with a high-quality [pond liner](https://pondacademy.com/pond-liners), but water often escapes around the edge instead. Settled soil or shifted landscape rocks can redirect water outside the liner, especially near a waterfall or stream.

Bring the pond to its normal operating level without overfilling it. Before adding municipal water to a stocked pond, use a pond-safe treatment labeled for the disinfectant your supplier uses, whether chlorine or chloramine. Treat the water before it reaches fish. With the pump running, walk the perimeter and check these common trouble spots:

- Low or folded liner edges
- Tight turns along a stream
- Both sides of a waterfall and places where rocks press down on the liner

Look at the surrounding ground for damp soil or pooling water. Moisture can narrow the search area, but water may travel through soil before it becomes visible. Plants or soil touching the water can also [wick water over the edge](https://pondacademy.com/pond-losing-water-causes).

If the edges remain dry while the pond continues to lose more water than the tub, move on to the controlled pump-off test.

### Step 2: Shut Down the Pump

If the pond has no circulation pump, mark its level after Step 1 and monitor the same point over a timed period without rain or refilling. Treat the container comparison only as a rough reference. For earthen ponds, use the structural warning signs in the repair section below to decide when site assessment is needed.

Turn off the auto-fill. Disconnect the pump and related equipment from a safe, dry location. Never enter the pond or handle wet equipment while it is energized. Pond equipment should use properly installed outdoor ground-fault circuit interrupter protection, commonly called GFCI protection. [OSHA explains how a GFCI responds to leaking electrical current](https://www.osha.gov/etools/construction/electrical-incidents/ground-fault-circuit-interrupters).

Protect Fish During the Test

An air pump helps, but it does not make every extended shutdown safe. Use this short shutdown plan to protect pond fish:

- Keep the test as short as practical. Start temporary aeration before stopping the main pump. If possible, provide pond-only circulation without running the suspected leaking circuit, and keep watching the fish even when a [pond aerator](https://pondacademy.com/pond-aerator) is running.
- Keep biological filter media wet and supplied with oxygen. Removable media can be held in aerated pond water when the filter cannot safely maintain flow.
- Stop feeding. Test ammonia and nitrite if filtration remains interrupted because ammonia can harm fish, as explained in [UF/IFAS guidance on ammonia in aquatic systems](https://ask.ifas.ufl.edu/publication/FA031).
- Move fish before falling water can strand them. Use a clean, fish-safe container filled with pond water and fit a secure, ventilated cover. Provide strong aeration, match the pond's temperature and avoid crowding. Beyond very brief holding, provide established filtration or actively monitor ammonia and nitrite in the container. Use conditioned replacement water as needed.

After switching off the pump, let the connected water features and filtration circuit finish draining back. Then mark both the pond and tub levels and begin the timed comparison. Check them frequently and use the shortest interval that gives you a measurable result. Never leave a stocked pond to drain unattended.

If the pond falls farther than the tub during the same period, excess loss is continuing. That points more strongly toward the basin or a connection that can leak without circulation. A stable waterline may narrow the inspection band, but it does not prove the opening is at that height. A bottom leak may continue draining. More than one opening may also be involved.

If the pond's drop becomes roughly equal to the tub's while the pump is off, but excess loss returns when circulation resumes, inspect the circulation system more closely.

If the tub and pond drop by about the same amount and neither step reveals escaping water, ordinary evaporation is more likely. An auto-fill may replace routine loss through a compatible fill-valve installation, but it must not hide unexplained water use. Monitor consumption so unexplained filling remains visible. Install locally required backflow protection. Treat every gallon of municipal water for the supplier's chlorine or chloramine before it reaches fish. The [EPA explains how chloramine persists in drinking water](https://www.epa.gov/dwreginfo/chloramines-drinking-water). [UF/IFAS fish-health guidance](https://ask.ifas.ufl.edu/publication/FA099) warns that municipal chlorine or chloramine can be lethal to fish if left uncorrected, and its [dechlorination guidance](https://ask.ifas.ufl.edu/publication/FA171) explains treatment options.

If you need help tracing a suspected opening, use only a purpose-made leak-detection dye whose current label permits use in a stocked pond. Keep the water still and use the label's specified quantity at the suspected opening. Observe its precautions, including whether fish may remain in the pond. Observe the labeled application area for movement toward an opening.

When the system can be restarted safely, inspect these areas while water is moving:

- [Pond skimmer](https://pondacademy.com/pond-skimmer) and external filter housings
- Waterfall boxes, stream edges, and nearby liner folds
- Pipe unions, valves, fittings, and exposed plumbing

Look for drips and wet ground instead of tightening every connection blindly. Overtightening can damage plastic fittings or distort a gasket.

Once a leaking component is identified, disconnect power and follow the equipment instructions to isolate flow and release pressure before opening it. Clean and inspect accessible unions or gasket seats. Reseat a displaced seal only if it remains sound; replace damaged seals with the specified compatible part. Replace cracked fittings, pipe sections, or housings instead of forcing them tighter. Follow the specified adhesive cure time before refilling and restarting, then check the repair under normal flow. Have inaccessible or buried plumbing leaks traced and repaired by a pond installer rather than excavating blindly.

## Pond Leak Repair

Identify the pond's construction and expose the damaged area before buying a repair product. The right [pond sealer](https://pondacademy.com/pond-sealer) or patch must suit the material and the conditions under which you can prepare and isolate the repair.

### Guide to Repairing Pond Leaks

#### How to Repair a Pond Liner Leak

Start by identifying the liner material, such as EPDM rubber or PVC. Inspect the surrounding liner as well as the opening. An ordinary patch needs sound surrounding liner. It may fail on brittle material or beside a damaged seam or fitting. There is no universal damage-size cutoff that determines whether a liner can be repaired.

Use only a repair system that specifically supports the liner material. Cleaners and primers must also be compatible because a harsh or unapproved solvent can weaken the liner. Ask an experienced pond-liner installer to assess extensive damage, failed seams, brittle material or inaccessible openings before choosing a larger repair or replacement.

##### Using a Compatible Underwater Sealant

1. Lower the water enough to reach the damage unless the sealant is specifically approved for underwater application in a stocked pond.
2. Remove dirt and loose material, then prepare the surface with the cleaner or primer approved for that sealant and liner.
3. Apply the sealant at the thickness required by its instructions and keep the area still.
4. Isolate uncured sealant from fish and pond water unless the exact instructions explicitly permit that exposure.
5. Wait for the full specified cure or isolation period, restore the water slowly, and monitor the repair.

An underwater sealant works best on localized damage that it can fully bridge and bond to. It cannot restore strength to brittle liner or fix a separating seam unless it is specifically designed for that job.

##### Using a Compatible Liner Patch Kit

1. Lower the water and expose enough sound liner around the damage for the patch to overlap it fully.
2. Clean and dry the area as required by the patch system, using only preparation materials supplied or approved for that kit.
3. Position the patch without stretching it and press or roll it firmly from the center outward.
4. Keep the patch isolated for its full bonding or cure period.
5. Refill slowly and repeat the tub comparison to check the repair.

A patch needs sound liner around the opening. If the surrounding liner cracks or separates, repair or replace the affected section rather than applying another small patch.

#### How to Repair a Concrete Pond Leak

A concrete crack may be limited to a surface coating, or it may reflect movement in the structure. Have a widening or repeatedly returning crack assessed before covering it.

For a stable repair area:

1. Move fish and isolate the work area from pond water. Use the temporary holding precautions in the shutdown callout above throughout the repair. Return fish only after the full cure and any required rinsing, with suitable water conditions.
2. Remove loose coating and prepare the concrete exactly as required by the repair system.
3. Apply compatible crack-repair material before adding a coating when the system requires both steps.
4. Wear the required personal protective equipment and work within the product's temperature and moisture limits.
5. Keep water and fish away until the repair has fully cured, then complete any required rinsing before refilling.

A pond-rated epoxy coating may waterproof properly prepared rigid surfaces, including compatible concrete applications. It does not correct ongoing structural movement. Use the exact product instructions to establish compatibility and prepare the surface. They also specify the mixing ratio and application conditions. Wear the required protective equipment and allow the complete cure time.

Product details were verified on September 21, 2026. For a stable, properly prepared rigid surface, [Pond Armor's current 1.5-quart Pond Shield listing](https://pondarmor.com/shop/pond-shield-non-toxic-epoxy-coating-1-5-quart-kit-white/) states coverage of up to 60 square feet at 10 mils. Rough or porous concrete can reduce coverage. Confirm the needed kit size from your measured area and follow the [current Pond Armor instructions](https://pondarmor.com/instructions/) rather than using the coating over an active structural crack.

Pond Armor Non-Toxic Pond Shield Epoxy Paint

[Amazon](https://www.amazon.com/Pond-Armor-SKU-WHITE-QT-R-Non-Toxic-1-5-Quart/dp/B00D2ZWLGQ/ref=as_li_ss_il?ie=UTF8&linkCode=li2&tag=pondacademy-20&linkId=21b26acc3f46f67369d905edea64142b&language=en_US)

This Pond Armor demonstration shows one approach to repairing a cracked concrete pond with Pond Shield Epoxy. Use the current instructions on the exact product for final preparation and cure requirements.

[Video on YouTube](https://www.youtube.com/watch?v=-CUVPUbD1UE)

#### How to Repair a Clay or Earthen Pond Leak

An earthen pond may lose water through permeable soil rather than one visible crack. Sodium bentonite is one possible treatment for suitable soil-seepage conditions because it swells when wet. Its effectiveness depends on the existing soil and how the material is placed or compacted. The [USDA Natural Resources Conservation Service pond handbook](https://www.nrcs.usda.gov/sites/default/files/2023-05/NRCS%20Agricultural%20Handbook%20590.pdf) explains why the sealing method must match the site.

Get qualified assessment before attempting a consumer repair when you find:

- Damage to a dam or embankment
- A leaking drainpipe or sinkhole
- Large animal burrows or active erosion

Before using bentonite, confirm that it suits the pond's soil and measure the treatment area. The exact bentonite product's instructions determine the application method and amount. Check its handling precautions and whether fish must be removed before treatment. Refill only under the stated conditions. Some methods require lowering or [draining the pond](https://pondacademy.com/how-to-drain-pond), mixing bentonite into exposed soil, and compacting the treated area.

This Natural Waterscapes video demonstrates one way sodium bentonite may be applied. The demonstration is not a site assessment; the pond's soil and construction determine whether that method is suitable.

[Video on YouTube](https://www.youtube.com/watch?v=2YSSOYQIgc8)

## Sources

- [Food and Agriculture Organization of the United Nations: Water Requirements and Water Supply](https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6705e/x6705e02.htm#21a)
- [U.S. Environmental Protection Agency: Chloramines in Drinking Water](https://www.epa.gov/dwreginfo/chloramines-drinking-water)
- [Occupational Safety and Health Administration: Ground-Fault Circuit Interrupters (GFCI)](https://www.osha.gov/etools/construction/electrical-incidents/ground-fault-circuit-interrupters)
- [University of Florida IFAS Extension: Ammonia in Aquatic Systems](https://ask.ifas.ufl.edu/publication/FA031)
- [USDA Natural Resources Conservation Service: Agriculture Handbook 590: Ponds - Planning, Design, Construction](https://www.nrcs.usda.gov/sites/default/files/2023-05/NRCS%20Agricultural%20Handbook%20590.pdf)
- [Pond Armor: Pond Shield Instructions](https://pondarmor.com/instructions/)
- [University of Florida IFAS Extension: Fish Health Management Considerations in Recirculating Aquaculture Systems-Part 1: Introduction and General Principles](https://ask.ifas.ufl.edu/publication/FA099)
- [University of Florida IFAS Extension: Chlorine-Friend or Foe?](https://ask.ifas.ufl.edu/publication/FA171)
- [Pond Armor: Pond Shield Non-Toxic Epoxy Coating - 1.5 Quart Kit White](https://pondarmor.com/shop/pond-shield-non-toxic-epoxy-coating-1-5-quart-kit-white/)
- [POND Trade Magazine - Demi Fortuna: The W.E.T.S. Method for Diagnosing Water Loss](https://www.pondtrademag.com/the-w-e-t-s-method-for-diagnosing-water-loss/)