Repairing Tennessee Lakes and Ponds: Beware the Polymers

Spending a small fortune to build a pond is a stressful process. Unfortunately, the stress level is often magnified when the pond begins to fill, and the landowner waits weeks and then months for the water to flow into the spillway…Only to realize in the end that his new pond has a leak. Most leaks can be prevented by hiring a pond builder who won’t cut corners; but if you find yourself with a leaky pond, avoid a second mistake and extra months and money wasted: skip the polymers.

There are several polymer products sold to pond owners to fix pond leaks. What do they all have in common? In our experience, they don’t work.

These products are marketed as being the cure-all miracle solution to pond leaks, but buyer beware: we know of several pond owners who fell for the marketing and used one of these products, only to see the leak return a month or three down the road. Some of these products have been around for decades, while others are relative newcomers to the pond market; what is consistent among these products is that when a new one appears, the marketing makes a point of pretending as though it’s an entirely new scientific development, as though there were not other identical or nearly-identical products that had been on the market many years, and it typically gets a lot of attention from pond owners who recently built a leaky pond and don’t know that these products have been around a long time. These products are marketed as requiring a fraction of the volume of more established, accepted leak-correction methods such as bentonite or clay; the much-smaller volume translates to much-smaller cost, and the pond owner thinks he has found the panacea for his problem.

Here’s the easiest way to understand why these products are not an effective solution to most pond leaks. Suppose you had a four-foot-deep above-ground pool that had fifty holes, each only a half-inch in diameter, in its floor. If you had to choose between a sheet of plastic one millimeter thick or a sheet two centimeters thick, which would you choose? The answer is obvious: the thinner sheet would tear within a day or two, while the thick sheet would hold for the rest of your life.

It’s the same principle in lining the bottom of a pond. Bentonite is applied at a minimum thickness of half an inch; clay is applied at a thickness of a foot or more. The material does indeed cost more in these volumes, but the volume of material is crucial in sealing the pond. A one-acre pond six feet deep holds just under two million gallons of water – that’s a lot of hydrostatic pressure bearing down on your expensive leak solution.

Most leaky ponds don’t have one isolated hole like a bathtub drain in one spot; the leak consists of poor soil that is too porous over much or all of the pond bottom. In effect, you have many small leaks rather than one big one. In cases like this, there isn’t a method to trace the leaks because they’re too small and too numerous; and the only way to mitigate them is by creating an impermeable layer above them. And that layer has to be substantial enough to last as long as you plan to own the pond (which is usually longer than a few months).