Aquatics Unlimited: Articles: Pond Construction
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Pond Construction

What materials are can be used to make a pond? 45 mil EPDM liners have quickly become the industry standard; they are affordable, flexible enough to allow better fit, fairly resistant to UV, and often carry a 20 year manufacturer's warranty. Other liner materials, including butyl rubber and PVC may be less expensive, but are often harder to install and less durable. Also popular are small preformed plastic ponds which are quite durable, but not as easy to install as they would appear.

Pond PhotoWhat is the difference between a 45 mil and a 32 mil liner, and which is better? "Mil" simply refers to the thickness of the material, so the 45 mil would be thicker and therefore stronger (assuming the same material). 45 mil liners are also usually made of EPDM and carry a 20 year warranties, while 32 mil are made of lesser materials with shorter warraties.

What is the purpose of an underliner? An underliner protects the pond liner from puncture by sharp objects such as stones and roots. Failure to protect the pond liner from punctures may void its warranty.

What can be used as an underliner? We offer an inexpensive commercial underliner; otherwise, a layer of sand, newspapers, old carpet or insulation could be applied.

What size liner would be required for a pond 7 feet by 14 feet that varies from 1 to 3 feet in depth? Start with the width (7 feet), add twice the greatest depth (3 feet + 3 feet), then add an extra foot or more for overhanging each pond edge. In this case the pond liner would have to be at least 15 feet (7+3+3+1+1) wide. Then do the same thing for the length, (14+3+3+1+1=22). The pond would need a liner at least 15 x 22, which could be purchased off a bulk roll, or as a standard 15 x 25 boxed liner.

What's the biggest size pond that can be made from a 10 x 15 liner - assuming a maximum depth of 2 feet? Starting again with the width, subtract twice the depth (2 feet x 2),then subtract another foot or more for each overhang, leaving a maximum pond width of 4 feet (10-2-2-1-1). Do the same thing with the length, leaving 9 feet (15-2-2-1-1) as the maximum length.

How many gallons does a pond 10 x 15 feet with an average depth of 1.5 feet hold? Make sure all measurement are in feet, then multiply length times width times depth, and multiply that total by 7.5 to get gallons (10 x 15 x 1.5 x 7.5 = 1687.5 gallons). This would be for a pond that was perfectly rectangular with perfectly vertical sides; an actual pond would probably hold considerably less water than the calculated amount. In addition, all pond measurements tend to be rather rough, so we would call this a 1600 gallon pond.

Can pre-formed ponds be used free-standing? No, they need to be dug in and back-filled. The entire pond bottom and all plant shelves need to be well supported to eliminate the possibility of cracking.

Home many hours of sunlight should a pond get per day? A minimum of four hours will keep most plants alive, but 8 to 12 hours will promote better growth and flowering.

Name some cautions about siting a pond near trees or in a low lying area. Trees produce roots that might pierce the pond liner, and leaves and other debris that might fall into the pond. They also shade the pond, which may limit plant growth. Ponds may also inhibit tree growth by restricting root development. Ponds in low lying areas can be contaminated by runoff such as lawn fertilizers and weed killers, and possibly overflow.

How deep must a pond be to keep fish in over the winter? How about plants? At least half the pond bottom must be an absolute minimum of 30 inches, 36"-48" would be even better. It's possible, but somewhat risky to over-winter in shallower ponds if a heater or pump is used to keep a portion of the surface free of ice.

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