Finding and Repairing Pond Liner Leaks

In ponds there will always be water lost from evaporation and sometimes splashing from water features and waterfalls. But if you notice the water disappearing faster than you think it should, you may need to investigate to determine if you have a leak or not.

Good quality pond liners have a warranty against damage from UV light. Usually they are guaranteed for 20 years, but because they are mostly covered from the sun you can expect the pond liner to last much longer than this. The cheaper PVC (“vinyl”) liners even come with a UV warranty, but because they are thinner they are more prone to leaks.

Damage to the pond liner usually occurs from external sources, such as people walking inside the pond, sharp objects falling on the liner, or roots growing up through the base of the pond. You can protect against roots by laying some good quality pond underlay on the ground before laying the liner down. Often people lay weed mat first, underneath the underlay which is an inexpensive way to get another protective layer before the liner. Weed mats help to guide roots away from the liner.

Finding the leak

If you think you have a leak, follow these steps to locate it

1.If you have a pond pump, the first step is to turn off the pump and watch the water level over the following 24-48 hours. If it continues to drop, the leak is in the main basin of the pond and not outside of the pond in a water feature or piping.

2.If the leak is outside the pond, check your plumbing joins and pipes for leaks, and the waterfall and stream. Usually the leak is caused by plant latter or other obstructions raising the water level above the liner, or stones settling and moving the liner. Check for wet spots outside the pond in these areas.

3.If the leak is in the main basin, allow the pond to empty to the point the level of the pond stays steady. Then you know the approximate level of the leak. If the level gets so low that fish and plants need to be removed, consider using a free standing pond to temporarily hold the plants and fish if there is insufficient water in the pond. Look for anything unusual from a pin prick to a large slit. 

How to repair the pond liner

There are a couple different methods, depending on your budget and time frame. In either case, clean around the hole first to remove dirt and algae using a rag.

For the first quick and inexpensive fix, you can fix the hole underwater using Gold Label Sealant, which is safe for fish and plants. Be sure to wear plastic disposable gloves, as this silicon is so sticky it will mark your skin for up to a week.

  1. Place the silicon in a caulking gun, and squeeze it into and around the hole in the pond liner.
  2. Smear the silicon over and around the hole.
  3. For a larger hole, cut a small piece of the pond liner from the edge of the pond and place that over the silicon to patch the hole. Ensure both pond liner surfaces are cleaned well first. The pond can be re-filled when you are satisfied with your repair work.

For a more certain repair, an EPDM Pond Liner Repair Kit or a PVC Repair Kit (for PVC only) is the way to go.

  1. Ensure the liner is clean and dry, and any wrinkles are smoothed out.
  2. Apply the primer to the area to be patched with the abrasive pad.
  3. Let it touch dry - when touched with your finger it should not stick and string as your finger comes away.
  4. Pull the paper off the patch and apply the patch smoothly.
  5. Roll to provide pressure on all parts of the patch.
  6. As an extra precaution, you can apply Gold Label Sealant to the side of the patch, and smooth it out.
  7. Leave for 24 hours before immersing with water.