Before reading this it is recommended you read about the causes of leaks as it will give you a better foundation of what to look for.
Causes of water loss in your pond
Step 1
Turn off the pump and all parts of your feature that move the water. Monitor your feature over the next several hours to see if water level changes. If the water level in your pond drops significantly go to Step 3. If the water level stays the same go to Step 2.
Step 2
You have now determined that the leak is not in the main basin pond. Now you need to narrow it down a bit further. The pond leak is either in the plumbing or in the waterfall / stream. Closely inspect your plumbing, particularly at any joints, make sure there is no leakage here. Next, inspect your waterfall and stream for leaks. Most of the time, the problem is caused by plant matter or other obstructions raising the water level and causing an overflow over the liner. Perhaps a stone has settled or your pond liner has slipped below water level in an area. If you did not read the causes of water loss it is highly recommended you read it now. If the ground is expected to be dry check the edges for moisture. If you find moisture you now have a good idea of where to look closer for the source of the leak. If you still have not found the problem use the ideas in Step 3 in the stream bed.
Step 3
At this point, you have determined that the leak is in the pond itself. Leave the pump off and allow the pond to continue to leak until it stops. If it does not stop before reaching a level dangerous to fish and plants, you will need to temporarily remove them from the pond. If they remain in the pond make sure they have proper aeration and your monitor them for problems. While the water level is dropping check around the edges to make sure that the pond liner has not sunken down or rocks have not been displaced. When the water reaches the point where it is no longer dropping it will be necessary to closely inspect the liner all along this water level to find the source of your pond’s leak. You should be looking for any irregularity in the pond liner from a large gash or a tiny pinprick. For fast leaks you can try putting some milk in a squirt bottle and spraying into the water at the edges of the pond. The milk will cloud the water where there is no hole. It will flow toward the hole, if there is one. This method will not work for slow leaks.
Once you have found the source of your pond leak it is time to make repairs. If it was just a displaced liner, move everything back into place. If the liner is damage it will need to be drained so it can dry and be repaired in that area.
If you are still struggling to find the leak I suggest reading and or rereading causes of water loss. If you are still struggling contact us and we can come take a look at it.
