Evaporation. This is the first thing to consider. The average rate of evaporation for a pond in South Jersey is approximately 1“ to 2“ per week. This will vary depending on the size of your pond, the temperature and humidity, the amount of sunlight it gets, and the extent of any waterfalls or streams you may have. Water evaporates faster when it has increased surface exposure across stream rocks and splashing falls. If you have a small 6‘ pond with a long stream or high waterfall it will drop much quicker than would a 25' pond with the same stream and waterfall. If you are experiencing water loss at a rate of multiple inches per day, then we can safely rule out evaporation as the cause. (Unless you are in the desert, we have heard of ponds in Phoenix that will have 3" of evaporation per day in the middle of summer.)
Click 'Read more' down on the right to see the full article...
Note: In a properly-built pond the liner will have been trimmed in excess, leaving about an extra foot of liner tucked behind the edges to easily allow for these adjustments that occur from natural settling of the soil.
Splashing. Another thing to investigate is splashing off the rocks in your waterfall or stream. Look for any places where the flow of water is splashing out beyond the liner. If it is, reposition the rocks on and below the waterfall so they direct the splashing within the bounds of the stream or pond. Another thing to check at this point is whether there is any clogs or obstructions in the stream that are backing up the flow and diverting water over the edge. This could be a build-up of algae or rocks, or possibly leaves and twigs that have fallen into the stream. If blockages such as these are present, simply removing them may be all it takes to solve your low water crisis.
If you’re still losing water at this point, then it’s time to do some more intensive investigating. This can be time-consuming and you may opt to call in the pros.
Now that we’ve ruled out the most common culprits and narrowed down the cause to a leak, it’s time to determine where that leak is located. The first thing to do is to turn off your pump. Let it sit for 24 hours and monitor the level in the pond. If it is steady, you now know the leak is isolated in the stream or waterfalls. If it has gone down, let it continue until it stops dropping. This will show you the depth where the leak is located.
Note: If you have fish in the pond, it is advised to place an aerator directly in the pond to maintain oxygen levels in the water while you perform the leak diagnosis.
If the leak is in the liner, there are two options at this point: patching the hole or replacing the liner. If your pond is older, it is possible the leak is the result of natural degradation to the liner from UV damage, animals, or shifting rocks. With these older liners, there may be multiple holes, and it is likely there will be more holes developing in the future. In those cases, we recommend putting in a new liner. Installing a new liner can often be done in a day, and will give you greater peace of mind and more time enjoying your pond.
If you believe the leak is a result of physical damage to the liner, possibly from someone or something falling in the pond or dropping a heavy rock, and the liner is otherwise in good condition, you may choose to locate the hole and apply a patch. For locating and patching a small leak, go around that level of the liner and remove any rocks, you will want to closely inspect the liner for any tears or punctures. These may be difficult to see; you can use some milk in a dropper to help identify where the leak is located, just squirt a little bit under the surface and see if it clouds or if it moves to the leak. When you find the leak, apply a patch, replace the rocks, refill the pond and enjoy. If the level stopped dropping above the bottom of the skimmer faceplate, you should investigate the skimmer to ensure the faceplate sealed correctly. Check behind the faceplate and feel for any wet soil around the opening of the skimmer. To learn the proper method for resealing the skimmer to the liner, scroll down for a link.
If you’ve inspected the pond liner and can’t find any leaks, the problem may be in the plumbing. You’ll need to inspect the pipe, the fittings, and the pump connections for any leaks. This is going to be difficult and messy work, and you may find it easier to just call in the experts.
Now that you know what to do when your pond is losing water, you can quickly determine if the cause is something relatively simple you can do yourself, or if it’s a more serious problem that might be better left to the pros who have years of experience in such matters. By following these steps, you can save time and aggravation and expedite the repair process so you can get back to relaxing and enjoying your water garden!
For resealing the faceplate of a skimmer, refer to page 6 of this PDF: