How to Fix a Leaking Pond Liner

Are your pond water levels dropping? Having to constantly top up your pond as you lose water? It’s a common occurrence and pond liner repair is one of those key skills you’ll learn over your time as a pond owner.

It’s not the easiest job in the world but it is necessary and it isn’t as complex as it might seem.

As repairing a pond is such an important part of ownership, we’re putting this guide together.

By the end of this page, you’ll have the knowledge and confidence to tackle a leaking pond liner and your fish will thank you for it!

Is your pond liner leaking?

Water levels fluctuate constantly within the average pond. You’ll see minor variations in water levels throughout the year and especially in warmer months.

This should only be a centimetre or two but may be exaggerated if you have fountains or water features.

If your water levels change just a few centimetres, it’s not likely to be a leaking pond liner.

If they fluctuate more than that, it might be.

How to find a leak in a pond

Would you believe us if we told you that you can localise a leaking pond liner using a ping pong ball?

It’s true!

If you’re confident you have a leaking pond liner, here’s what to do.

1. Turn off all your pumps, waterfalls and water features and top up your pond to its normal level
2. Place a ping pong ball in the water
3. Monitor your pond over a couple of days to check water levels. If the water level stays the same, chances are it's your pump, waterfall or water feature that has the leak
4. If the water level reduces, monitor where the ping pong goes as it will be pulled towards the leak
5. Mark the area where you think the leak is ready for repair

If you definitely have a leak somewhere and it stops when you turn off your pump, waterfall or water feature. Remove them one by one and check the pipes and device for leaks.

If you have a leaking pond liner, the pull of the water as it escapes will pull the ping pong ball towards it. The ball is so light, any resistance within the water will attract it.

As the escaping water will create a current, that current will work on the ping pong ball and pull it towards where the water is escaping.

Repairing a pond liner

Once you know roughly where the leak is, you’re going to need to remove your fish so you can repair it.

We suggest buying a cheap inflatable paddling pool and placing it next to your pond. Fill it up with pond water and transfer the fish to it.

You now have two options.

You can wait until the water level in your pond stops falling. This will give you a line where the hole likely is. The water level will stabilise once below the hole, so once that happens, you can further localise the leak.

Or, you can fully empty the pond until you can get up close and personal with the area of liner you think has the leak.

Either way, expect to spend some time identifying where the leak is.

Once found, circle it with chalk so you don’t lose it!

Pond liner repair is quite straightforward once you have found the hole. What happens next depends on the size of the leak and how many there are.

If there are multiple leaks due to age or wear in the liner, you should consider replacing it.

If it’s a single hole and the liner is otherwise in good condition, a repair should suffice.

Use either pond liner jointing tape, liner repair sealant or a pond liner repair kit on the hole or tear.

• Pond liner jointing tape - Ideal for small holes or tears and splits above the waterline. Only really useful for small repairs and needs careful preparation of the site for proper sealing.
• Pond liner repair sealant - Good for small holes and tears and is easy to work with. Mainly useful for small repairs and will take 8 hours or more to go off.
• Pond liner repair kit - Like a puncture repair kit for bikes. Good for small holes and tears but needs a dry liner to work effectively.

The pond liner repair kit is probably the best option. If you have ever repaired a puncture on a bike, it’s a very similar process.

Kits are cheap and readily available and are almost invisible once applied. You will need to wipe down the liner and dry it thoroughly before applying though.

Any of the above solutions should stop your pond leaking. We would recommend partially refilling your pond above the repair line and leaving a day or two to monitor water levels.

Use the ping pong ball again if you like, but monitor levels carefully to make sure that was the only leak.

Once you’re confident you no longer have a leaking pond liner, return the water and the fish to the pond.

As you can see, pond liner repair takes time and needs your full attention but there’s nothing technical or difficult about it.

The hard part is identifying where the liner is leaking. The actual pond leak repair is the easy part!