Mil vs. Gauge (GA)
When buying a swimming pool liner, it is very important to verify if the thickness measurement of the vinyl you are being quoted for is in Mil or Gauge.
It is important to note that a Mil is a standardized measurement that can be measured with a micrometer, where a Gauge is not. One Mil is equal to an exact .001 of an inch. A 20 Mil liner is .020 of an inch thick, and a 25 Mil liner is a little thicker at .025 of an inch thick. One Gauge, on the other hand, can mean different things from one manufacturer to the next. Some will use Mil and Gauge interchangeably and this might not be correct.
Most reputable swimming pool retailers sell their swimming pool liners measured in Mil.
Above ground liners usually are between 20 and 25 Mil.
Many online retailers sell their liners measured in Gauge, they want you to assume that a 20 Gauge liner is the same as a 20 Mil liner, when in fact it is almost always a thinner liner. Unless they specifically say their 20 Gauge liner is 20 Mil thick, then you should assume it is not.
You will also want to verify if the liner is the same measurement on both the sides and bottom. Some liners are thicker on the bottom, and a little thinner on the sides. While this is not necessarily a bad thing, you just will want to verify what the retailer is offering, so you can be sure you are comparing apples to apples and know exactly what you are paying for.
Embossed vs. Non-Embossed Embossed vinyl liners vary in thickness. The thickness of an embossed pool liner is measured from the thickest point of the liner or the high point of the embossing, rather than the thinner valley, which is the true thickness of the liner. Simply put, a 20 Mil embossed liner is not 20 Mil but in fact thinner.
Pool Pros Recommendation: Buy a non-embossed liner from a reputable local dealer, measured in Mil. Better yet, buy your pool liner from Pool Pros!