Flexible liners are available between 20 mils (and lower), up to 60 mils and beyond—but the 35 to 40 mil range is ideal for most farm ponds. At the 20 mil and below range, these liners are generally useful for backyard ponds and hobbyists who want to create a water feature they can enjoy but one that won’t necessarily be highly trafficked. For ponds that will see livestock or equipment traffic, 30 mils is the minimum that you should consider.
For large scale farm ponds, 45 mil liners are recommended because they’re tough enough to stand up to the enormous weight of the water above them while minimizing seepage and potential leaks. At the 60-mil range, these liners are generally used for the most extreme jobs, like oil and gas storage where leaks must be prevented at all costs.
