30-Mil vs. 20-Mil Pool Liners

How Liners are Measured

• Liner manufacturers express the thickness of pool liners using the terms "gauge" and "mil." These terms represent the same thing but they are not necessarily equivalent. For example, 30-gauge indicates a thickness of .0260 inches, or .6604 millimeters, and 30 mil indicates a thickness of .0275 inches, or .6985 millimeters. The same is true for 20 gauge and 20 mil - the measurements are close, but not the same. Higher gauge or mil numbers indicate a thicker material.

20 mil

• Liners with a 20-mil thickness are approximately .0205 inches thick and are actually quite durable. These liners are often used for pool floors or other areas not subject to extensive wear and UV exposure. 20-mil liners will be less expensive than 30-mil liners from the same manufacturer but almost always include the same warranty.

30 mil

• Liners with a 30-mil thickness, or .0275 inches, offer additional durability in areas of a pool subjected to extra wear. These areas include pool sides, particularly with ladders, where swimmers enter and exit the pool. Additionally, they offer added protection from harm caused by UV rays, which will ultimately cause the liners to become brittle and crack.
  Before selecting a 30-mil liner it is important to realize that although they stand up better to certain conditions, they are also more stiff and difficult to bend, so making corners or tight transitions with them can be difficult and can cause premature wear.

How to Decide

• Although the urge to overbuild and select the thickest liner possible may be strong, this could be a poor choice in the long run. Look for areas in the pool which may receive more wear than others or may receive extended exposure to the sun. These areas will be candidates for a 30-mil liner. Likewise, look for areas where tight bends or transitions are necessary and consider 20-mil liners for these applications.