Thickness Isn’t as Important as Installer and Manufacturer
As a pool liner installation specialist I have sold over 3000 pool liners and installed or managed the installation of each and every one of them. Over the past ten years I have been able to observe the longevity of different kinds of liners and I have reached the following conclusion based on my observations. The thicker liners (27 or 30 Mil) will last about one year longer than the thinner 20 mil liners. I bring this up because the average customer tends to think that the thicker liners are significantly better than the thinner liners. While the thick liners are a better choice it is not the thickness you should be concerned with when choosing a pool liner based on quality / longevity.
The two most important considerations when choosing a pool liner are the installation crew and the manufacturer of the liner. Not the sales person but the actual crew that will be installing the liners. I often have customers ask me if I will be installing the liner myself. I tell them that I would never subject them to such pain and agony. My crew is 10 times better than I am at installations and therefore they are the ones you want doing the work. The Lazy Day installation crew has installed all 3251 pool liners for Lazy Day over the past ten years and they have become very good at what they do. Most pool companies install 2 or 3 liners a year and view it as a side business. Recognize that the more you do something (anything) the better you become. This is true with almost every activity and pool liner installations are not exception to this rule.
The manufacturer is another major factor in the quality of the installation because the quality in liner manufacturing varies greatly across the industry. It is best to stick with the larger manufacturers like Kafko or Tara Liners. These manufacturers have multi-million dollar pieces of equipment that precision cut and weld the liners. The technology of the smaller manufacturers just can’t provide the same level of precision. Precision in making a great liner is key.
Also, the larger manufacturers tend to offer better warrantys against seam separation.