The most common lining materials in use today include:
PVC (Polyvinyl Chloride)
– This highly flexible, synthetic product is not always safe for plants and fish—only “fish grade” PVC is nontoxic. Because most PVC liners are not resistant to ultraviolet (UV) radiation, they typically must be covered with one foot of soil to prevent degradation. Also, PVC liners have a history of cracking in cold temperatures. This can contribute to their short life span, which averages less than 10 years.
HDPE (High Density Polyethylene)
– This is a thermoplastic material with a 20-year lifespan in most water feature applications. Its benefits include durability, stability and chemical resistance. Although it’s safe for aquatic life and relatively inexpensive, HDPE has the least flexibility of all pond-lining materials, making it difficult to work with during installation, especially in colder climates. This rigidity can limit one’s design creativity for decorative water features.
EPDM (Ethylene Propylene Diene Terpolymer)
– This high-quality, durable geomembrane material provides several key benefits, including installation ease, exceptional weathering characteristics, plant and fish friendliness, outstanding UV resistance (even in direct sun exposure), and outstanding elongation, which allows for creative and demanding water feature designs. With a 20+ year lifespan in exposed applications and 30 years when covered, EPDM is a cost-effective solution for multiple climates and environments.
Factors influencing which liner is right for your project include size, shape and type of water feature; year-round climate, proximity to wildlife and budget—both for the immediate installation, as well as longterm use and maintenance.
Advantages of EPDM geomembranes
With millions of square feet installed globally, EPDM is among the most widely used lining materials. It is a user-friendly and safe material to install. Because it’s not stiff or rigid like some other lining materials, EPDM is easier to handle in the field and conforms better to changing slopes and surface irregularities.
Additionally, the variety of panel sizes—ranging from 8' wide x 10' long for small projects to 50' x 200' panels for large, commercial applications—make EPDM an ideal solution for many different situations. EPDM seaming uses highly engineered and tested primers, and elastic tapes that require no special tools or utilities. Some of the other products require expensive, difficult to operate heat welders.
EPDM’s flexibility is not only an asset when designing water features with non-geometric shapes that add to the look and feel of the surrounding environment; it’s also ideal in a formal water feature application. In a formal feature, the EPDM panels can easily be adhered to the walls with bonding adhesive, water block seal, termination bar and lap sealant, yielding beauty and longevity.
Beyond its long-term benefits, EPDM panels typically require only minimal year-round maintenance and, if necessary, they are among the easiest materials to repair. Repair kits are readily available and the process is similar to repairing a bicycle tire.
A quality installation
Although each water feature is uniquely different, many of the same installation steps are required. Once excavation is complete, including removal of all rocks, roots and other debris from the subgrade, it’s time to install the lining material. It is highly recommended that all water features incorporate a top quality lining product of adequate thickness, such as PondGard or EPDM Geomembrane from Firestone Specialty Products, Indianapolis, Indiana. While PondGard is only available in a 1.14-mm-thick (0.045") membrane, Firestone EPDM Geomembrane is available in 1.14 mm, 1.52 mm (0.060"), and 2.28 mm (0.090") thicknesses. Best practices call for the liner to be used in conjunction with a 4.5-oz. to 16-oz. nonwoven, needle punched, polypropylene geotextile underlayment, to ensure the integrity of the water feature. The underlayment increases the puncture-resistant characteristics of the liner, while providing geogas venting and groundwater relief options, from under the liner, preventing floating of the liner.
The lining process begins with laying down the underlayment and placing the geomembrane liner over it, leaving any excess lining material overhanging the perimeter of the excavated area. During this process, many water features, particularly ponds, require that the geomembrane be folded to make it fit properly. It is critical that all folds in the lining material run perpendicular to the water line and not parallel, in order to maintain a proper water level. If the folds run parallel, it will lower the holding level of the pond to the lowest part of the fold. The inherent flexibility of EPDM makes it easy to handle folds and allows the liner to be shaped to fit numerous design options, from basic to near infinite complexity.
On large ponds, where more than one panel is needed, the fastest and most secure method to join panels together is to use a seam tape, (such as Firestone’s QuickSeamO Tape System). Seam tapes provide superior strength, elongation and are easy to install accurately for dependable, long-term performance. The QuickSeam tape system’s strong initial bond strength grows even stronger with time in temperatures ranging from -40°F to more than 175°F, even under water.
For projects where a waterfall is desired, once the underlayment and geomembrane are in place, connect a rigid PVC pipe or flexible PVC hose from the skimmer to the waterfall; install the check valve, auto fill valve and pump, and assemble the plumbing and electrical wiring, making sure that all connections are watertight and secure. Finally, seal the liner securely to the skimmer’s face plate using the skimmer’s sealant and compression to ensure proper functioning of the unit.
Once the liner and all operating systems are secured in place, landscaping may begin. Using a variety of natural materials is the best practice—such as a combination of decorative or distinctive rocks, mulch and indigenous plants—in order to avoid an unnatural appearance. Avoid the “string of pearls” appearance, where only one size and/or shape of rock is placed in a row around the entire perimeter giving it a very odd, unnatural look. To create a more visually striking and natural-looking water feature, place larger rocks varying the size, shape and color. Next, cover the exposed liner with small river rock or gravel—then fill in around the larger rocks with mulch and plants.
In the bed of the water feature, place the aquatic plants in the planting pockets and cover the roots with coarse soil, calcine clay or cat litter. These materials help hold the plants in place, and they work far better than regular soil. If installing a waterfall, use cap stones to form the waterfall; use mortar or urethane foam to seal between stones and direct the water over the falls.
Once the landscaping is complete, wash soil off the rocks and conduct test flows over the rock weirs. Be sure to pump out the dirty water—using a separate debris pump—and refill the water feature with clean water. Leaving dirty water in the pond can damage the water feature’s pump and filter. As a final touch, install landscape lighting and properly connect the electricity. Once everything is up and running, fish or other aquatic life can be added.
Building a better water feature— one that seamlessly integrates into the environment—requires a combination of good planning, quality products and sound installation practices.
EDITOR’S NOTE: Bill Johnson is with warranties and field services of Firestone Specialty Products.