FINDING A LEAK IN YOUR POND
The primary function of any pond is to hold water. Leak checks are a vital part of any start up. For a still pond the obvious question is "Does it hold water?" If so then everything is set to go. If it doesn't, then it is a simple matter to allow the water level to stabilize and then inspect for damage at the stable water line wherever it may be. Lowering the pond level an inch or two below the stable water level will allow some additional space for inspection. Careful inspection is in order for all ponds. Inspect liners for deterioration from ultraviolet exposure or physical damage (IE: puncture holes from rocks, rodent damage, & low liner areas. Tubs and preforms should have no problems due to weather conditions, but may need some adjusting of level or backfill to support the container. Concrete ponds in freezing climates may have been subject to freeze damage or settling if not on a firm foundation.
The key issue for many ponds is finding the exact leaking area. Whenever there is a system that moves water out of the basic container (IE: Waterfall & Stream) there is a risk of leakage. Often these leaks can be difficult to detect because of the nature of the pond, filter, stream or other feature. Ask: When was the leak first noticed? How often is water added? Is there an automatic fill device? Is there any damage or settling? Is animal damage a possibility? Children playing in the pond or stream, or well-meaning landscaping near the pond may result in leakage as well.
Next, take a walk around the pond to look for any obvious wet areas, filled soil berms or retaining walls that may be subject to settling or movement. Gradually increase the detail of the inspection as obvious possibilities are ruled out. If the details of construction are known, the inspection of obvious possibilities can be ruled out. Then the inspection can focus on finding the leak. For ponds of unknown construction, the inspection may need to include some additional details about the pond to know exactly what to look for. Keep in mind that splash or evaporation should be less than five gallons per day for the average water feature of about 8 x 10 feet. This amount can be scaled for smaller or larger features.
1.) Bottom Leak - The first way to test for a leak is to turn off the waterfall system and check to see how far the water drops. If it drops all the way to the bottom of the pond, then we know for sure that the leak is on the bottom of the pond. This could be caused by a bottom drain or sharp rock edges. It would be suggested to place your fish in another place while checking this.
2.) Side Leak - If the system is off and the water level drops and seems to stay at a certain point, then there is a side leak. The best way to find a side leak is to wait until the water level stays at that certain point, fill the water garden up a 1/2" or so and go around the edges with a food grade dark colorant or a cap full of milk. By doing this you will be able to see where the dye travels out of the water garden. You may have to shift some rocks around in order to locate exactly where the leak is. A liner patch will easily fix these types of leaks.
3.) Waterfall/Stream Leak - If you turn off your waterfall/stream/pump system and the water level doesn't drop, then the leak is somewhere within that system. It could be water spilling over the edge of a stream instead of going back into the pond. The fittings on the waterfall or filter could be leaking. The Flex PVC or kink free tubing from the pump to the waterfall/filter could be leaking.
If you think you have found a leak in the containment (pond), you can use a few drops of dairy products like cream or milk to confirm the leak. Place the small amount of dairy product in the water near the possible leak. The dairy product will form a cloud in the water in which you will be able to observe any current movement. If there is a hole in your liner, the cloud will be pulled towards and through the hole. If a leak is confirmed, then lower your water level and repair the leaking area. Repeat as necessary until you have found all of the leaks. (Yes, sometimes there can be many) You can also do this process with food coloring. TJB-INC prefers dairy products because the beneficial bacteria in the pond will breakdown any organics left after the testing is done and will clean the dairy cloud from the water.
Isolating the Water Garden systems (IE: Pond, Waterfall, Stream, or Plumbing) is the key to finding the leak point. If the leak appears when the pump is running, then turn off the pump to see if the containment (pond) leaks at all. Be sure to start with the pond filled to the overflow point. Even very small cracks or holes can leak substantial amounts of water. Allowing the pond to stand overnight will either identify or eliminate the basic containment (pond) as the leak point. Small leaks may take a long time to reach a stable level. To speed up the process, it may be helpful to pump out a few inches of water and then re-check for a constant water level. By lowering the level a few inches at a time, a relatively narrow band of pond containment can be isolated for inspection.
If the basic containment (pond) is intact, the next step is to isolate any other system components to check for leaks. Piping and filters can be checked by filling the system and shutting off the pump with a check valve, gate valve, or pipe cap to prevent back flow and then watching that part of the system to see if the level drops. This operation can be done at the same time the basic containment (pond) is being checked.
If there is a waterfall or stream, that part may best be examined with the system in operation. Installed liners make this process easier since any leakage will probably be at the edges. As needed, a hose or pipe can be placed in longer streams starting at the bottom to isolate portions of the stream to check for leaks. Concrete watercourses without liners underneath may be subject to leakage through cracks or settling of the stream bed.
Once the leak is isolated, the correction is usually quite simple. If there is liner damage, a patch appropriate for the liner type will provide for a permanent repair. Component or piping leaks are usually a simple repair or pond edges are often a simple fill or restructure and replace any decorative stones or plants. Depending on the time of construction and the nature of the site, the first winter may have significant settling of berms and edges. These areas are the first place to look for leaks and often are the source. Edge leaks will generally leave evidence as wet spots along the edge. Dry days are the best for checking pond integrity.
The obvious goal is to build ponds with no leaks from the start. By building a pond with a variety of "inspection points" around the edges, it can be very simple to check pond edges for adequate liner height. - Fold some liner under the edges to have some additional liner available if settling occurs or the owner desires some small modifications. Also check for liner folds that may allow for channeling of the water. TJB-INC has found this to be a major cause of pond leaks. Any folds should be perpendicular to the edge of the pond or steam. Folds at an angle may have a section that sags below the water level and produces a leak path. Also be sure than liner folds in the stream overlap downhill like roofing shingles to prevent channeling in the stream bed.
For those involved with concrete construction, placing a rubber liner under the concrete structure will prevent leakage in the event of any cracks in the concrete shell. Even concrete with applied coatings can benefit from being installed over a liner. Any waterfall or stream should have a liner that overlaps the basic water containment (pond).
If you determined that the leak is in the pond and you still cannot locate the leak, there is one more test you can do. It is called Reverse Leak Detection and will only work with liner ponds. You will have to remove all the water in the containment (pond). Then uncover a small section of liner at the top edge of the containment (pond). Lift the liner away from the soil so you can place a hose down along the outside of the liner. Turn your hose on and pour some food coloring or dairy product down the alongside the hose. What you are going to do is to put colored water between the dirt and the liner. The bottom center of the liner should start to rise like an inflated balloon as the water level rises. Pay close attention and look for colored water leaking into the now dry containment (pond). Mark and repair any areas where colored water has come through the liner. Be careful not to allow the colored water (between the liner and the dirt) to rise above the top edge of the liner and spill into your dry containment (pond). You will not be able to find your leak(s) as easily. This Reverse Leak Detection can be done with or without rocks in the containment (pond).
Sometimes, it just gets too frusterating to find the leaks and you just want to pack it in and give up. All is not lost. As long as the leak is a slow leak, you can add an automatic waterfill or just top off the water when the level gets low. For water gardens with fish, it is recommended to do a partial water exchange on a weekly basis. If you have a small leak, this will create your partial water exchange automatically saving you from having to pump out water each week. This is not called giving up but making lemonade out of lemons.
