bullfrog.gif - 2414 Bytes banner.gif - 627 Bytes

Back Contents Main Glossary Next

Frog-friendly backyard

Flexible pond liners

Size of your flexible liner

It is best to decide on the type of liner you wish to buy and see what sizes it comes in before you decide on the shape and size of your pond. A number of bulk liner rolls come in increments of 1.5 m starting at the 3 m width. If a homeowner has dug a pond and needs a 4x7 liner, he/she would have to buy a 4.5x7 m or 7.5x4 m liner according to the above widths.

Measure the length and width of the rectangle that your pool fits in. Add twice the maximum depth of your pond and a metre to each of these measurements and you have the size of the liner you need.

1 + ( 2 X maximum depth) + length = length of liner in metres
1 + ( 2 X maximum depth) + width = width of liner in metres

Types of Flexible Pond liners

There are generally four types of flexible pond liners: 40 -80 mil PVC sheeting, rubberized pool liners, 45 mil High Density Polyethylene (HDPE) liners, and, our recommendation, 45 mil Ethylene Propylene Diene Monomer (EPDM) liner. Most of these liners are manufactured in black and natural tones of brown and green creating a more natural look for your pond.

  1. The 40-80 mil PVC liners with ultraviolet inhibitors have a lifespan of 10 years or more and are non-toxic to pond life. PVC liners may crack along the folds during the winter, and have poor patching ability.

  2. Butyl rubber pond liners are UV resistant and generally have a 20 year lifespan. Some types of these liners contain toxic ingredients that may leach into the water. These liners are not readily available, very expensive, do not come in many sizes and are difficult to patch. Butyl rubber liners are flexible, but the 40 -50 mil weights are thick and are hard to fold at corners and curves.

  3. HDPE liners are very stable, non-toxic, have the same life expectancy as PVC but cost 1/3 the price. HDPE liners are not readily available, are difficult to work with in cold climates, and come with no guarantee.

  4. EPDM (45 mil) liners are flexible, U.V. stable, resistant to air pollution, have a lifespan of 20 years, are non-toxic to pond life and are very inexpensive. This liner type is actually more flexible than PVC, therefore making it easier to install. Picov's Watergardens will only sell the EPDM 45 mil rubber liner to their customers because "It has proven itself to be the best liner for our cold climate."

Putting in Flexible Pond Liners

Before placing the pond liner you should remove all sharp objects and make sure the soil is packed down hard and level. Once a pond is put in, the bottom should be covered with 2-10 cm of washed sand topped with a layer of gravel.

When you build your pond try to pick a sunny day with no rain in the forecast for a couple of days. Sun makes digging more fun, but also warms up the liner making it a little more malleable. Do not leave your liner out on the grass in the sun, because the heat generated by the liner can kill large areas of grass. Before installing a flexible liner you should check it for manufacturing defects (holes and weak points), and line the pond excavation with 5 cm of sand or a geotextile layer. It is not recommended to use old carpet or newspapers as carpet bulks up in the corners and makes for difficult and unsightly folds in the liner, and newspaper has the potential to get soggy and become penetrable to sticks or rocks.

It is advisable to have four people to help you place your flexible pond liner. Each person can take a corner and make sure the liner is equal at all areas over the pond. A flexible liner is installed by placing it over the hole and it is held firmly with either a line of bricks or paving stones. Place a garden hose in the middle of the pond and fill with water. The weight of the water settles the liner to the shape of the pool. When the pool is filling with water, someone should be in it with their shoes and socks off helping the liner fold in the corners. They should also insure that the liner is not being pulled down unevenly which can create a potential leak when the pond is filled up to level. There is no danger of the liner snapping back under water when the weight is off because it is kept firmly in place by water pressure. This is the time to make final adjustments such as levelling the liner edge or to direct overflow to the intended area. Tuck the edge of the liner under 15 cm of soil or keep it hidden underneath stones.

We have been advised that if some flex is left in the liner after installation, the liner has less tendency to rip and allows you to work in the pool.

Back Contents Main Glossary Next

credit image map