Vinyl liners are used in nearly all above ground swimming pools and many in-ground pools, as well. Made of PVC, they can come in a variety of thicknesses, designs, and patterned prints, all of which effect the overall price.
The thickness of a vinyl liner is measured in either mils or gauge. Yes, there is a difference.
A mil is the equivalent of one thousandth of an inch (0.001). Most liners range between 12 and 28 mils, with 20 mils being the industry standard.
So what's gauge?
In some industries, gauge values get smaller as the material gets thicker. Take sheet metal, for example. 10 gauge sheet metal is twice as thick as 20 gauge. With vinyl, however, it is the opposite. As the gauge value increases, so does the thickness of the vinyl.
Manufacturers that represent their vinyl liners in terms of gauge often use the same numerical values as those that use mils, creating a bit of confusion when it comes to purchasing one.
When shopping for vinyl liners, keep in mind that mil is slightly thicker than gauge when given the same value. (20 mil liners are thicker than 20 gauge.)
So thicker vinyl is better, right?
Not necessarily. Although thicker vinyl might seem stronger, the most important factors that determine a liner's longevity are proper fit, the water chemistry in the swimming pool, and UV exposure in direct sunlight.
Above Ground Liners
There are three types of above ground liners: Overlap, J-hook, and beaded.
Overlap liners are the least expensive and most common liner type found in above ground pools. They work much like a trash liner works in the waste can in your home. Covering the bottom, they stretch up and over the lip of the pool, "overlapping" to the outside. They are usually clipped to the wall with plastic trim strips called coping, which can either be round in shape, or flat.
Unibead liners are basically j-hook liners AND beaded liners at the same time. The chosen style will depend on which one works with your particular swimming pool. Some unibead liners are J-hook right out of the box, but by "peeling away" a portion of material from the edge of the liner, it becomes a beaded liner instead of a j-hook. Other unibead liners have the beading at the edge of the liner, on top of the j-hook, so there is no cutting, no peeling.
In a vinyl-lined in-ground pool, beaded liners are by far the most common liner type used. The bead track is usually built into the coping around the interior lip of the pool or fastened externally to its surface. Once seated, the wedge-shaped beading at the top of the liner is forced into the bead track, securing the liner into place.
Inground liners are commonly custom made, so if you are looking for a replacement liner, we recommend that you contact a local professional to measure the swimming pool and help you select a new liner. If you provide your own measurements and are wrong, you might not get your money back, since the liner was made exclusively for you.