Step 1: Design the pond and gather materials
A backyard pond doesn't have to be big to have a big impact. This pond is less than 6 ft. long and just over 4 ft. across. But with its striking stone surround and sparkling waterfall, it can become the centerpiece of any landscape.
This design is versatile, too. You can make the pond twice as large as ours or half the size. You can locate it on flat terrain or tuck the stone waterfall wall into a slope. And unlike most ponds, this one won't leave you with a small mountain of soil to deal with—you can simply use the excavated soil to form a berm behind the waterfall wall.
This pond will take anywhere from one to three weekends to complete. The size of the pond is one factor in how long it will take. But the stone you choose is also a major factor (for more on that, see “Set the stone,” below). Our cost for the basic pond materials, including the liner, filter and pump, was about $500. The stone may be free if you can collect it yourself or it can cost up to $1,000 if you choose expensive stone at a landscape supplier.
This article won't tell you everything you should know before you grab your shovel. See other articles on this site for a guide to pond planning, including advice on choosing a site. Electrical codes require a GFCI-protected outlet to power the pond's pump. To see how to run underground wiring and place an outlet anywhere in a yard, search this site for “outdoor outlet.”
Figure A: Pond and Waterfall Details
Soil left over from digging the pond hole can be used to create a berm behind the tank. Then add plants to give the waterfall a lush backdrop.
Most home centers carry only a small range of pond supplies. For the best selection, visit a large garden center or landscape supplier. To get acquainted with the vast array of choices, go online and search for “pond supplies.” Here's what you'll need:
EPDM rubber liner: Make sure the material is at least 45 mil thick. To estimate the size, add twice the depth of the pond to the length and width. Then add 3 ft. to both the length and the width. Finally, add the height of the waterfall to the length.
Underlayment: This feltlike synthetic material provides a protective cushion under the liner. Buy the same amount of underlayment as liner. Pump: Pumps are sized by the amount of water they can move, measured in gallons per hour (gph). One way to select the size is to plan on 100 gph for each inch of waterfall width. We wanted a 5-in.-wide stream of falling water and chose a 500-gph pump.
Miscellaneous: 12-in. waterfall tank, filter media, pump basket, lava rock, black foam pond sealant, silicone caulk, pea gravel, tubing and connectors sized for your pump.
Tip: Before you shop for water plants at a garden center, browse online to learn about your plant options. Just do a search for “water plants.”
Step 2: Dig the pond hole
We dug our pond in a kidney shape, but you can make yours any shape you like. To experiment with different shapes, lay out a garden hose or rope. But plan for the total size of your water feature. The surrounding stone will extend 1 to 2 ft. beyond the water's edge on three sides, and the waterfall wall, tank and berm will cover 3 to 4 ft. behind the pond. When you find a shape you like, cut through the sod around the perimeter with a spade to mark the shape. Then start digging.
Toss the soil toward the back and sides of the pond where you'll later build up the berm. Be sure to throw the soil far enough so you don't have to move it a second time. When you reach a depth of about 1 ft., create ledges along the sides of the hole. Carve the ledges into undisturbed soil; don't try to build them from soil you've already dug up. Make the ledges at least 1 ft. wide. These ledges help prevent cave-ins and provide a shelf for plants that prefer shallow water. Slope the vertical walls of the hole slightly, about 1 to 2 in. per vertical foot. Don't make the bottom of the hole perfectly level. Instead, slope it slightly toward the end of the pond farthest from the waterfall (about 1 in. of drop per horizontal ft.). That provides a low spot where you can place the pump and make it easier to drain the pond. Level the rim of the hole so the surrounding stones will all rest at about the same height above the water level (Photo 1).
Step 3: Line the hole with EPDM rubber
The pond liner is made of tough EPDM rubber, but it's not puncture-proof. So inspect the hole before you line it. Cut back any protruding roots and dig out any stones. If the soil is filled with stones, spread an inch of sand over the ledges and bottom. Next, line the hole with “underlayment,” a thick synthetic fabric that cushions the liner against damage. Overlap sections of underlayment by about 6 in. and run the underlayment at least 1 ft. beyond the rim of the pond.
Lay the rubber liner over the pond and then push it down so it roughly conforms to the inner shape of the hole. Kick off your shoes and work in your socks when you're on the liner to avoid puncturing it. Make sure the liner extends at least 1 ft. beyond the edge of the pond on three sides. On the waterfall side, you'll need enough excess to reach the height of the waterfall. You'll run that extra length of liner upward behind the stone to keep water in and soil out. When the liner is in position, start filling the hole with water, and work out the wrinkles as the pond fills (Photo 3). Once water covers the liner, the pressure won't allow any “dewrinkling,” so stay on top of the task. Most important, don't leave any gaps between the soil and the liner.
Step 4: Set the stone
Surrounding the pond with stone can take just a few hours or a whole weekend, depending on two things: First, it depends on the shape of the stone you're using. Stone with flat surfaces, like the flagstone we used, stacks up quickly. Rounded or irregular stone requires lots of trial-and-error puzzle fitting and triples the work. The second variable is neatness. We chose a rough, informal look, with protruding stones and fairly wide gaps between them. A more formal, even and uniform look will take a lot longer to achieve.
Before you begin, lay out the stones and hose them off to keep dirt out of the pond. Set aside three or four large, flat stones as options for the waterfall ledge and the cap that will cover the waterfall box. Then surround the pond with stone, overhanging the water by a couple of inches to hide the liner (Photo 4). Use fairly large stones that can't get accidentally kicked into the water. You can set stones directly on the liner, but a 1-in. layer of gravel makes leveling the stones much easier. Be sure to use rounded “pea gravel” rather than gravel containing sharp pebbles. We laid two courses of stone at the front of the pond, but one layer of large stones is enough to hold the liner in place.
As you build the waterfall wall, loosely drape the liner up against the stone and pile soil against it. When you reach the desired height of the waterfall, connect the supply tube to the waterfall tank and attach the liner to the tank (Photo 4). Next, set the waterfall ledge stone in place. Slowly pour a bucket of water over it to make sure the water flows off and into the pond. If the stone needs more tilt, shim it with chips of stone.
Step 5: Assemble the waterfall tank and pump
Set the tank in place over well-packed soil or stones, with the outlet resting on the waterfall ledge. Then build up stone around the waterfall ledge (Photo 6). You can hide the tank with soil or stone. We used both and left one side exposed so we could easily disconnect the supply tube. That way we can pump all the water out of the pond for repairs or cleaning. Cap the tank with a stone that's large enough to cover it but small enough to move easily.
Connect the pump to the supply tube, set in a pump basket and add lava rock. The lava rock provides a home for bacteria and keeps debris out of the pump. Set the pump and basket at the end of the pond farthest from the waterfall. That way, water will circulate through the entire pond before being pumped back to the waterfall. Place the filtration bag in the waterfall tank and start up the pump. Watch the water flow at the waterfall. Some of the water may run back along the underside of the ledge stone instead of falling directly into the pond. If so, create a drip line by running a bead of clear silicone caulk along the underside of the stone about an inch from the edge. If the water is dirty, disconnect the tub from the waterfall tank, pump out as much as possible and refill the pond. If the water is still a bit murky, just give the filtration system a few days to do its job.
Bacteria Clean the Water
There are lots of ways to keep pond water clean and clear—chemicals, high-tech filters, UV light systems. Some pond owners skip all of these and simply change the water a few times each summer as it becomes green or cloudy. We chose a “biological” filtration system for our pond. The lava rock in the pump basket and the “filtration media” (a bag of plastic strips) in the waterfall tank simply provide plenty of surface area where bacteria can grow. The bacteria consume decaying leaves, fish waste and other stuff that would otherwise make the water murky and feed algae. In addition to being inexpensive and eco-friendly, biological filtration is easy. All you have to do is remove the filtration media twice each year and slosh it around in a bucket of pond water (tap water will kill the bacteria).