When purchasing a liner for an in-ground pool, there are dozens of patterns and colors to choose from. I’m not offering any advice on patterns or colors, except to say that a darker liner will heat water in a swimming pool faster than a lighter color. The advice I am offering is on liner thickness. Most liner manufacturers produce liners in at least two thicknesses-20 and 27 mils. A 20 mil liner is thinner and less expensive than a 27 mil.
The cost difference is usually around $250 to $400 more for the thicker liner. If you feel you need the thicker liner and cost is not an issue, then buy the 27mil liner. However, if the price does matter, don’t get talked into the more expensive liner if you don’t need it. The best way to explain it is that whatever is going to cut or tear a 20 mil liner will also cut or tear a 27 mil. 95% of the liners I have installed in the last 20+ years have been 20 mils.
In my own swimming pool, I have a 20 mil liner. The colors will fade at the same rate and the warranties are usually the same. If you have a condition in your pool that requires a thicker liner (extremely rough walls) then purchase the thicker liner. If not save your money and don’t get talked into the more expensive pool liner, you’ll never notice the difference.