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Everything You Need to Know to Build the Perfect Backyard Pond

Want to introduce an attractive new dimension to your landscape? Just add water. The experts at This Old House explain what it takes to create a handsome, thriving aquatic centerpiece for your backyard

All About Ponds

Photo by Jerry Pavia

There's something about water in motion that soothes the soul. Watching light play off the ripples or listening to the splash of a fountain—these are universally calming pastimes. It's no surprise, then, that one of the most popular landscaping projects for This Old House readers is installing a pond.

Happily, you don't need deep pockets or lots of land to enjoy your own water feature. You can install a fully equipped, landscaped, fish-filled pond for around $500, provided that you do your own digging. Creating a lush habitat like the one at right requires rubbery liners, powerful pumps, effective filters, and, without question, a commitment to care for them. But when you're finished, whether it's tucked into a corner of the yard or next to a deck or patio, your pond will provide an endless source of fascination for family and visitors alike.

Pictured: Built close to the house, this pond creates a refreshing, relaxing backdrop just out the back door. The rock waterfall makes a pleasing sound as it oxygenates the water. Plants soften the stone edges and provide cover for fish.

Anatomy of a Pond

Illustration by Rodica Prato

A clean, healthy pond requires a few key elements to keep water contained, fresh, and filtered.

Water agitator

Keeps water oxygenated. Fountains, waterfalls, and bubblers are all agitators.

Filter

Cleans the water coming from the pump.

Liner

Prevents water from leaking into the ground.

Underlayment

Protects the liner from punctures and stretching during installation.

Pump

Circulates water through the filter and up to the waterfall or fountain.

Covered GFCI outlet

Feeds power to the pump. Trips automatically to prevent lethal shocks.

Vitals

Photo by Kolin Smith

What's it cost?

Home-center kits start at $70 for a simple 9-square-foot, 84-gallon pond. A more typical 176-square-footer installed by a pro starts at $5,000, while more grandiose versions can easily exceed $50,000.

DIY or hire a pro?

Ponds longer than 6 feet on a side and deeper than 18 inches require so much digging and other heavy work that they are best left to pros. Smaller ponds are good DIY projects, but let pros handle the plumbing and electrical work.

How long do they last?

It all depends on the liner. The best ones have a 20-year warranty and 30- to 40-year life span.

How much maintenance?

The electricity to run a pump for a typical 176-square-foot pond costs about $260 a year. Filters need frequent cleaning. A pond-maintenance firm starts at about $1,000 a year.

Type: Natural

Photo by Jerry Pavia

Meant to blend in like an integral part of the landscape, this kind of pond has free-form edges that don't

follow a straight or predictable course, and incorporates stones and plants native to the area.

Type: Seminatural

Photo by David Massengill/Cornerhouse Stock

Taking cues from the existing hardscape around a home, this most popular pond type has free-form edges set next to a brick, concrete, or stone patio. The plants can be native or not.

Type: Formal

Photo by Tim Street-Porter

Defined by geometric shapes, this style of pond is often edged in expensive mortared stone or poured concrete. Perfect for a reflecting pool in a formal garden, it also makes a fine showcase for fish. Plantings are sparse or nonexistent.

Where to Put It?

Photo by Kolin Smith

The location of a pond determines its health and your ability to enjoy it.

How much sun?

Ideally, ponds should receive sunlight in the morning and shade in the afternoon. This keeps the water cooler, discouraging algae blooms.

What about overhanging trees?

A tree's afternoon shade is welcome, but a pond directly under a tree's branches will quickly clog with leaves, seeds, or needles unless given constant maintenance. If a nearby tree is young, factor in its mature spread before settling on the pond's location.

How far from the house?

Ponds that are out of sight tend to get neglected. And if they're farther than 20 feet from your patio, you likely won't hear the gurgling of a waterfall or fountain.

What do the codes say?

Ask your local building department about how far a pond has to be set back from property lines.

Where are the utility lines? Dial 811 to have their location marked. This is a free service.

Materials: Liner

Use these formulas to calculate how much material you'll need (all dimensions in feet):

Liner length=pond length+(2 x depth)+2.

Liner width=pond width+(2 x depth) +2.

Multiply liner length by liner width to get total square footage.

Synthetic rubber

The best choice for most ponds, 45-mil-thick EPDM comes in sheets up to 50 by 200 feet. Durable, UV resistant, and flexible to -40 degrees F. Not to be confused with roofing EPDM, which has additives that kill fish.

About 67 cents per sq. ft.; GrayStone Creations

Plastic

Liners made of polyethylene (PE) and reinforced polypropylene (RPP) are thinner, lighter, and less expensive than EPDM but stiffer and harder to work with. Sizes up to 40,000 sq. ft. Like EPDM, they carry a 20-year warranty. Avoid PVC liners; they have a short life span when exposed to sunlight.

20-mil PE, about 30 cents per sq. ft., and 36-mil RPP, about 45 cents per sq. ft.; Pond Liner

Equipment: Pump

At minimum, the gallons per hour (GPH) rating should match the volume of your pond. A pump will need additional GPH to supply a waterfall or fountain, and enough "head" to push water to the top of that waterfall or fountain. Look for the unit with the lowest wattage; it will cost the least to run.

Direct drive

These heavy-duty units, which were the first pond pumps, are able to move lots of water. They also use the most power, and if their seals fail, they can spill oil.

GPH: 1,500–16,000.

Head: up to 52 feet.

Watts: 150–1,500.

Warranty: one to two years.

Cost: $200—$1,400. PondScapeOnline

Magnetic drive

Much cheaper to buy and operate than direct drives but without nearly as much oomph.

GPH: 65–3,000.

Head: up to 15 feet.

Watts: 25–350.

Warranty: six months to three years.

Cost: $45—$300. Danner Manufacturing, Inc.

Hybrid drive

Combines the power of a direct drive with the energy efficiency of a magnetic drive. Won't spill oil.

GPH: 1,200—10,000.

Head: up to 25 feet.

Watts: 110—500.

Warranty: two years.

Cost: $185—$500. Atlantic Water Gardens

Equipment: Filter

One type keeps water free of debris so that the pump won't clog. The other removes chemicals that harm fish. To sustain fish, you'll need both types or a product that puts both in one package.

Mechanical

Traps debris before it reaches the pump. Clean weekly in spring and fall, every other week in summer, monthly in winter. A filter in a waterfall or a surface skimmer will be easier to reach than one on a pump at the bottom.

$60—$800. PondScapeOnline

Biological

A must for ponds with fish. Bacteria living on a porous medium digest toxic nitrites and ammonia. Wait six to eight weeks for them to become established, or buy a starter colony. No cleaning needed.

$140—$500.

Equipment: Water Agitators

A pond will become a stagnant, algae-filled eyesore if you don't keep its water moving and aerated. Here are three ways to stir the pot:

Fountain

Water shooting up from the surface of the pond or flowing from a man-made ornament is visually compelling and nice to listen to. Available in a variety of sizes and shapes, each linked to a particular pump capacity.

Waterfall

To create the show you want, measure its width in inches at the point water spills out. Multiply by 50 if you want a trickle of water, by 100 for a sheet of water, and by 200 for Niagara Falls. The result is how many GPH your pump needs for the falls alone, not counting the pond.

Bubbler

An air pump, a separate device from a pond pump, produces bubbles that subtly ripple the pond's surface.

DIY Kits

Most online retailers bundle the pond essentials. Or you can buy a prepackaged kit from a home center that includes a rigid plastic tub, flexible tubing, and a properly sized pump. These kits are small and manageable enough to install in a weekend, but they don't include the biological filter you need for fish. Though you could add such a filter, they're really intended to be low-maintenance water features for people who want the pleasant sound of trickling water near a deck or patio, not a full-fledged ecosystem.

Shown: Beckett 65-Gallon pond kit, About $150; The Home Depot

Prep for Installation Day

Photo by Kolin Smith

Do you want fish? If so, build your pond at least 24 inches deep. That depth keeps the pond from freezing in winter or overheating in summer. In extreme northern areas, the minimum depth should be 3 feet.

Will you need a fence? In some areas, local codes mandate that yards with ponds deeper than 18 inches be surrounded by a fence with a locking gate to keep out unsupervised children.

How will it be refilled? Ponds must be topped off periodically to replace water lost through evaporation or splashing. You can do the job manually with a garden hose or have an auto-fill valve connected to a buried water line. When using city water, protect your fish by adding a dechlorinator directly to the pond.

What about the leftover dirt? Digging even a small pond will create a large pile of soil. A hired installer should get rid of it for you, but if you dig your own hole, use the soil to raise the grade around the pond or to build a waterfall.

Where's the power? A weatherproof GFCI outlet to power the pump should be located at least 10 feet from the pond. The electrical cable leading to that outlet needs to be buried at least 18 inches deep.

Pro advice

Rather than slope the sides of a pond right down to the bottom, make a shelf about 18 inches wide and 18 inches below the water's surface all around the pond's edge. This shelf serves as a platform for plants and a convenient step for anyone who falls in.

Demi Fortuna, August Moon Designs, Stony Brook, N.Y.

Pond Plants: Cattail

Photo by Mark Harmel/Getty Images

(Typha latifolia)

Zones 3—10

Grows along pond edges, in moist soil or shallow water. Hollow stems carry oxygen to the root zone, and to fish, year-round. Perennial; spear-like foliage grows up to 10 feet tall.

Pond Plants: Lotus

Photo by Wildlife GMBH/Alamy

(Nelumbo sp.)

Zones 4—10

Planted in containers up to 2 feet deep, it blooms on a stalk high above the water's surface. Perennial; leaves up to 20 inches in diameter sway on stems that grow up to 6 feet tall.

Pond Plants: Iris

Photo by Deni Brown/Getty Images

(Iris versicolor)

Zones 3—9

Plant in pots in 3 inches of water. Bears 5-inch-wide flowers in shades of blue or purple on 24-inch stems. Tolerates partial shade. Perennial; arching leaves grow up to 30 inches tall.

Pond Plants: Water Hyacinth

Photo by Hiroshi Tonoshiro/Getty Images

(Eichhornia crassipes)

Zones 9—11

A free-floating plant, it sends a 9-inch spike of lavender flowers up from a rosette of leathery, glossy green leaves. Perennial in Zones 9–11; often grown in colder climates as an annual.

Pond Fish: Goldfish

Photo by Robert Van Der Hilst/Getty Images

(Carassius auratus)

The ultimate in low-maintenance, goldfish can get by eating the plants, algae, and larvae they find. They'll live about 10 years and often grow up to 12 inches long.

Pond Fish: Koi

Photo by Kaz Chiba/Getty Images

(Cyprinus carpio)

Koi often live for 40 years or more and grow up to 3 feet long, depending on the pond's size. They must be fed regularly; you can even train them to eat from your hand. They'll survive winters as far north as Maine.

Solutions to Common Pond Problems

Photo by Olson Photographic

Algae:

You can kill this green slime with chemicals or UV lights, but it will still come back. You'll get better results by adding plants, barley straw, or biomat filters, and not overfeeding the fish.

Mosquitoes:

Keep the biters at bay by stocking larvae-eating fish, such as goldfish, mosquito fish, or bitterlings. Tossing in mosquito dunks with Bacillus thuringiensis (Bt) also kills the larvae without harming plants or animals.

Pests:

Deter raccoons with a straight drop of at least 18 inches from the pond's edge. Nylon netting stretched over

the surface discourages fish-eating birds. Motion-activated sprinklers may scare off other interlopers.

Leaves:

In the summer, sift out debris before it reaches the pump with a skimmer (about $116; Aquatic Ponds). Come fall, scoop out the bigger batches of leaves and needles with a pond net (about $22; Amazon).

Ice:

Place an air bubbler (about $40; Pond Biz Pond Supplies) or a floating pond heater (about $47; Gold Crest Distributing) into the corner of the pond to keep a portion ice-free and maintain a proper balance of oxygen and carbon dioxide.