One of the more popular questions that we get when dealing with liners is: "Are the thicker liners better, for my swimming pool?" I wish this was as easy as a yes or no answer but it isn't. There are a few things that actually factor in how to choose the right liner for you and your pool.
What is a mil for a pool liner?
When talking about the “mil” of vinyl pool liners, you should first understand what this terms actually means. A "mil" is a unit of measurement equal to one thousandth of an inch. So, a "20 mil" liner is equal to 20 thousandths of an inch. To put it into perspective a standard sheet of paper is 10 mil.
27 mil liner and Thicker: The Good
27 mil liners may be a good choice for your swimming pool if you have poor floors or walls. Example: If you are in need of covering up an old concrete swimming pool, it may be in your best interest to use the thicker liners. This also may be a good option if you have a lot of cracking on the surface of the floor or jagged points. Obviously the liner installer should smooth out the floor and grind down any jagged areas to protect against puncturing. But with our experience in these scenarios we have found once concrete begins to crack and shift, it is not just going to stop. So, if you simply cannot replace the floor for what ever reason you always have the option to install the thicker liner. This is truly an area where you should have your local pool expert come out and perform a site inspection first, to see if the liner will work properly.
27 mil liner and Thicker: The Bad
The thickness of your liner will play a huge roll on how the liner fits the pool shape. Speaking to many manufacturers we have found that thicker liners simply can not stretch properly with bends, curves or even tight corners of a pool as a 20 mil liner can. If a liner can not conform to the pool properly a couple of issues can occur.
Over stretched pool liner:
Pool liners are made to stretch slightly into curves and tight corners. Research from Tara Manufacturing shows if the liner is over 20 mil thick, the liner will not press against the steel wall or the vermiculite floor properly. In particular the corners of the wall and the corners where the wall meets the floor, leaving a gap between the liner and its backing. A good rule of thumb to remember is: a liner is only as good as its backing. This typically applies to damaged floors or walls, but I am applying it to this scenario because if the liner is pulled off of the corners, there is no backing at all. This leaves an opportunity for a puncture to happen in that specific area.
Dry Rot - If a liner is over stretched and pulled off of the pool wall, the liner will also begin to dry out more quickly. The gap between the liner and the wall creates a lot of heat, forcing the liner to dry up quicker and become more brittle. Which could eventually lead to a premature rip/tear.
Cost - Most manufacturers have to charge more, because there is more material because its thicker.
20 mil pool liners: The Good
20 mil liners are proven to stretch perfectly against tight corners and conform to the curves of a shaped pool. Minimising opportunity for punctures or drying out. They are also strong enough to withstand the weight of the water.
20 mil pool liner: The Bad
20 mil liners are not always made with certain prints depending on the manufacturer. So you may find a pattern that you like and it may only be made in a thicker size.
There it is guys the truth about vinyl liners! So before you order your next liner think about some of the things that I just said and make sure your liner is the right fit for your pool.