Guest Author - D. J. Herda
As you prepare your pond site for the liner, make sure you remove or blunt any sharp rocks or other objects that could punch a hole in your pond. If your pond site is “rough” or "lumpy," you might benefit from a pond underlayment, the equivalent to a carpet pad, in order to protect the liner from punctures. The underlayment is a second waterproof layer of protection against punctures and leaks.
Once you’re ready for the liner, measure the pond at its widest point. The results are the length of liner and/or underlayment you’ll need. Use a flexible rule so that you can run the tape from the top of the bank on one side, down into the deepest part of the pond, into any other depressions along the way, and up to the top of the bank on the other side. Keep the tape as tight to the walls and bottom of the pond as possible for accuracy. Take note of the measurement and add another four feet to your results. That figure will be the length of the liner you’ll need to buy.
For example, if your measurement turns out to be 14 feet, adding four more feet will give you a total of 18 feet in length.
Next, measure the pond at its shortest point, as above, and add four feet to the results. That will be the width of the liner you’ll need. Liner and underlayment most often are sold from large roles, available at home centers, nurseries, and pond-supply shops. The width of the roles varies. If you determine that you need a liner measuring 18 feet in length by 11 feet in width, and the liner comes in 8-foot, 12-foot, and 18-foot widths, you’ll need to buy 18 running feet of the 12-foot wide liner or underlayment. Always buy more, not less, than you think you’ll need.
That brings up the question of what pond material to buy. Liners are commonly available in PVC (Plasticized Polyvinyl Chloride), Polyethylene, and EPDM (Ethylene Propylene Diene Monomer). Of the three, by all means, buy the EPDM. It’s the most flexible, easy to work with, and giving in conforming to irregularities in your pond. It also has the best puncture and abrasion resistance of the three. In fact, EPDM liners are so durable, most come with a 20-year warranty.
Once you’ve purchased your liner, you’re ready for the installation. This is where you’re going to need some help.
Unfold the liner so that it’s flat on the ground. Bribe two or three neighbors to help you out. With four people, have each one take a corner and walk the liner over to the pond site, where you can center it over the hole before laying it in. If you have only two people, fold the liner in half and walk it to the site. Align the fold over the center of the site, lay the liner in, and unfold it.
Next, take off your shoes and climb in. Using your hands, work from the center out to remove as many creases as possible. You won’t get them all out, because you’re fitting a two-dimensional object into a three-dimensional space. Push the liner into all of the holes and crevices, trying to “use up” as much of the material as possible. Depending upon how carefully you measured, you should have between 1 and 2 feet of excess fabric hanging over the bank.
Climb out of the pond, get the garden hose, and fill the liner to a depth of about 1 foot. The weight of the water will help draw the liner into ever nook and cranny. At this point, if you’ve made plans to install a bottom drain, you should remove the water using the hose as a siphon. (If not, you can continue filling the pond.) I know it sounds ridiculous—wax on, wax off—but trust me on this. It’s the right way to do it.
Installing the Center Drain
Once the water is out, use some old rags to wipe dry the liner above the drain. Take a sharp knife and make a cross-shaped incision near the center of the drain. The cross should be slightly smaller in size than the diameter of the drain.
Next, squeeze a generous amount of silicon on the drain flange beneath the liner and thread the drain up through the hole, tucking the four corners of the liner underneath. Squeeze another generous bead of silicon on top of the liner around the cutout area so that when you place the flange on the drain and screw it down, the silicon will be sandwiched between the flange on both sides of the liner.
Now you have a drain with two layers of silicon to act as a water barrier--one below the liner and one above. Tighten the flange down as much as practical and wipe off any excess silicon from the liner. Allow the silicon to dry for at least 24 hours.
While you wait, you can complete the connections between the discharge pipe, your filter box, and the pump. (Or you can do what we usually do at this point--go out and spend a bunch of money on plants.) After waiting 24 hours for the silicon to cure, fill the pond to capacity, sit back, and enjoy.
Check out D. J. Herda's two latest gardening books, Zen & the Art of Pond Building and From Container to Kitchen: Growing Fruits and Vegetables in Pots, both available from Amazon.com.
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