Most water gardens are considered "closed systems" because water is recirculating vs. constantly coming in and out. That means there are only a few ways water can actually escape.
If you think your pond is leaking water, you can perform a leak test, which uses a process of elimination to help you locate the problem area.
How to Perform a Leak Test
Step 1: Answer these questions:
Does your waterfall pump have a PVC check valve or backflow preventor?
Does your pond have a waterfall filter box with the plumbing coming directly into the bottom of the filter chamber?
If you answered yes to the two questions above see steps below, otherwise proceed to Step 3.
Step 2: Check your waterfall box and connections, underground plumbing, and check valve.
Turn the recirculating pump off.
Ponds with check valves and waterfall filter boxes should remain full when turned off. If the waterfall filter box does not remain full, make sure the check valve is working properly, restricting water from entering back into the pond. A faulty check valve will make a gurggling sound indicating that water is escaping the plumbing and typically re-entering the pond back through the pump itself. If so, you must repair the check valve or buy new to continue the leak test.
Note: A temporary solution to a faulty check valve is to insert a plug or cap over the plumbing, and fill the waterfall filter manually to determine if the plumbing holding or leaking under the ground.
If the waterfall filter level remains constant at the brim of the waterfall box, then:
a. Your waterfall box itself and connections hold water and are ok.
b. Your plumbing underground is ok.
c. Your check valve and any plumbing outside your liner are ok.
Step 3: Check your pond liner and mechanical pond skimmer connection.
- With the pump off, fill your pond to your normal and desired level.
- Mark the water level with a coin. Set the coin on a rock just below the water level - if the water drops below the coin, it will be dry, if not, it is shinny enough you can see it and the water above it.
- Keep pump off for 12-24 hours, take second reading.
If your pond remains full with no water loss then:
a. Your pond liner is ok.
b. If you have a mechanical pond skimmer installed then the sealed connection is water tight and ok.
Step 4: Check your waterfall stream.
If your waterfall, the plumbing and the pond all hold water while the pump is off then there is only one other way water can be lost. Water loss can occur when the pump is on and water is in motion. This is typical around the sides of a waterfall or the sides of a stream.
Note: 99% of all leaks occur due to settled liner or water being diverted over the liner's edge. Rarely are holes in a liner the culpret to a pond losing water, especially if a pond has held water on a consistent basis prior to the occurance.
What to look for when you have determined the area of the possible leak:
a. Concentrate on the left and right of each waterfall area.
b. Visually identify all edges of the pond liner along the waterfall or pond stream.
c. If possible, reach behind the waterfall liner feeling for moisture.
d. Identify chipmonk tunnels or areas where rodents may be interfering.
e. Inspect noticeable areas where rocks have shifted.