Determining Liner Size

• The first and most important factor in selecting your liner is determining the size needed for a particular pond. Although EDPM liners are available in pre-measured lengths, these packaged liners are best suited for ponds smaller than 8 feet in diameter and with a depth less than 1.5 feet. If your concept pond calls for larger dimensions, it is often recommended to purchase your liner by the square foot. Due to the unusual shape of most ponds, determining the size of your liner can be a difficult task. It can be simplified by using the following formula:
  
  Length plus two times the depth, plus 2 feet, multiplied by the width plus two times the depth, plus 2 feet, equals necessary liner size.
  
  It may sound complex, but here's how to find the pond's dimensions: Place your pond within an imaginary rectangle, including the farthest points of the pond, and measure the distances between all four points of this imaginary rectangle. The depth of the pond is only limited by what your concept calls for. The formula provides a 1-foot excess around the perimeter.
  
  As example, a pond with an imaginary rectangle measuring 15 feet by 10 feet with a 1.5-foot depth would need a 20-foot by 15-foot (300 square feet) liner. Or: 15 + 1.5 + 1.5 + 2 = 20 feet long by 10 + 1.5 + 1.5 +2 = 15 feet wide.
  
  

Installation

• After completing excavation of your pond, place a 1-inch to 2-inch layer of sand down to act as a cushion between the excavated bottom and the liner. Aside from smoothing out the excavated area, the sand will help to prevent sharp rocks in the dirt from puncturing the liner. If you plan on having large rocks or boulders around the perimeter of the pond, prepare a concrete pad, roughly 4 inches to 6 inches thick depending on the weight of the rock, to provide a solid foundation and prevent the rock from tearing the liner. Next, place a layer of underlayment, a thick cloth-like fabric, to further protect the EPDM liner over the excavated pond. Finally, lay the EPDM liner down onto the excavated pond. If possible, lay the liner down on a sunny day, as the liner will be more compliant when warm.
  
  

Other Considerations

• EDPM liners can be purchased from many sources such as specialized pond and waterscaping suppliers, swimming pool retailers and home improvement centers. However, if you plan on stocking your pond with fish, you must select a liner that is fish-safe. EPDM liners intended for swimming pools or roofing may have additives that inhibit algae or mold growth. These additives are extremely toxic to fish or plants and should be avoided. If you are uncertain if a liner is fish-safe, refer to the packaging label or consult the EPDM liner dealer.