How to Stop a Pond from Leaking [Full Guide]

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So you have a nice outdoor pond and you might have doubts that your pond is leaking somewhere.

In this article, I will help you identify and fix pond leaks. Will guide you through the most common issues and will teach you how to fix a leaking pond yourself.

Fixing a leaking pond is not easy, especially if you never did it before. Let’s dive in and find out how to stop a pond from leaking.

Find and Fix Pond Leak

The most difficult part in fixing a pond leak is to find the actual leak itself. Fixing the leak is relative easy.

When it comes to leaking pond, there are few problem sources that come first:

  • Drain – it is not very common, but it is the hardest to fix
  • Filter – leaking filter can also cause significant water level drop in ponds
  • Pond liner – will deteriorate over time and needs to be repaired
  • Evaporation – sometimes there is no leak, just the evaporation is more significant

How to Fix Leaking Pond Drain

Smaller pond might not have a drain, but bigger ponds usually have it.

Leaking drain does not happen with new ponds, but often with old ones.

Usually the seal between the pond liner and drain pipe deteriorates and breaks over time.

A leaking pond drain is also very hard to identify, because the water which leaks out goes directly into the ground, having no visible sign besides dropping water level.

Leaking drain can be a nuisance, because usually you need to empty the whole pond in order to fix the leaking drain.

In this case, you need to catch all fish from the pond and deposit them in a good environment, where they can survive. You can use huge plastic barrels with air-stones to give your fish a temporary home.

While you drain the whole pond, it is a good idea to keep some of the water in order the keep some of the beneficial bacteria.

The filter of your pond should also be running in order to keep the colony of nitrifying bacteria intact.

After the pond is empty you can start repairing the leaking drain.

You need to clean and dry the drain. The best is to take the whole drain apart and reseal it again completely.

Once you’ve fixed the leaking drain and the silicone is cured, you can test it. Add water into the pond, just enough to cover the drain. Mark the water level and let it sit for few hours. If the water level stays the same, it means you did a great job sealing the drain.

Now you can refill the pond with fresh water.

Please remember, that your pond will need to go through a new cycle. You will need to monitor ammonia, nitrite and nitrate level until it gets established again.

Leaking Pond Filter

Most ponds have an external filter. Some larger ponds have very complex filtering system. If there is a lot of piping involved in the filtering, there is a big chance that somewhere will start leaking.

In full sunlight check the filter and pipes for any leakage. It is important to have bright light, because it is easier to identify any leak this way.

Once you find the leak, stop the filter. If you can fix the leak without draining the filter is better. This way you will not kill the beneficial bacteria from the filter.

If there is no other solution, but to totally drain the filter, place some water in a clean separate container and put all your filter media in it. Do not expose the filter media to air for too long, because all the bacteria which are cleaning your water will die off.

After you are done sealing the filter, refill it with water and check if there is any other leakage source on your filter. If there is no leak, place the filter media back.

Check your filter regularly, because through a leaking filter can lose a lot of water from your pond.

How to Fix Leaking Pond Liner?

Pond liners are made of very robust material. However, over time pond liners can deteriorate and break, mostly where they are stretched.

The first step is to find where the liner is leaking. Here is a great video that demonstrates how to find a hole in the pond liner:

Mark the current water level and check back in 24 hours to see if the water has dropped. If the water level is the same, most likely the leakage is over that water level.

Sometimes the leaking hole is very obvious; however most of the time is hidden under algae.

Scrub any algae, calcium or detritus from the liner. For this you can use any plastic card or a piece of wood. Do not use any sharp tools or material that might further damage the liner.

Once the hole is identified, you can go ahead and fix it.

If the hole is above the water level with just few inches, you will need to drain some water from the pond in order to give yourself more space to work.

To fix the hole, you will need a piece of liner and some glue. The best is to get a pond liner repair kit (I found this cheap repair kit on Amazon to be very good). This repair kit contains all the materials you need to fix a tear in the pond liner, and it is safe for fish.

Before applying any glue or self-adhesive material to the pond liner, you will need to clean and dry the surface of the liner first. This step is very important if you want to do a good and long lasting sealing job.

After fixing the liner, allow the glue to cure. You might need to wait at least a day before refilling the pond.

After the glue is cured, you can refill the pond with fresh water. Mark the water level again and check back after 24 hours. If you did a good job, the water level should be the same.

Water Evaporation

Water evaporation is a natural process of every pond. When the weather is warmer, the water evaporates faster.

Often beginners can’t identify whether their pond is leaking or only the water evaporation is causing the water level to drop.

It is normal that in the summer, when the temperature raises the evaporation is more significant. Due to evaporation the water usually does not drop more than couple of inches weekly.

Water evaporation helps keeping the water cool. You should not cover the pond in the summer to prevent water evaporation.

Covering the pond in the hot summer to reduce water evaporation can be catastrophic.

Water with temperature over 89 °F (32 °C) has very low oxygen level. Most fish, especially koi will not survive in low oxygen level water.

By covering the pond you are also preventing oxygen exchange, not only water evaporation.

So, do not cover your pond, especially in the summer. Just add fresh, dechlorinated water to maintain the water level.


I really hope that my article has helped you identify the problem and fix your leaking pond. I know that sometimes it is very hard to fix a leak and requires a lot of time and effort, but don’t let a leak discourage your from continuing this beautiful hobby.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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