What is a Pool Liner?

A swimming pool liner is essentially a sheet of vinyl custom fitted to cover and waterproof the floor and walls of your pool.

First vinyl liners were invented in 1950s and were quite a novel technology. They required an entirely new pool construction method, but because they were quickly adopted as the superior choice for the majority of residential applications, vinyl liners promptly took over the market and today lined pools are far more numerous than other in-ground pool types in Canada, US and Western Europe.

The cost of a lined pool is significantly less than a concrete one, a liner can be installed faster and generally lasts over 20 years in moderate climates, such as southern Ontario.

Even in hot sunny conditions, for example in California, liners are still the more popular choice, despite their shortened lifespan: due to the strong southern sun, a liner lasts only 7 to 12 years there, after which it must be replaced.

Liners are made of chlorinated PVC thermoplastic and can withstand a wide range of temperatures. Modern Liners are UV-resistant and generally have algae inhibitors added.

How do Pool Liners work?

Liners are secured only at the outer edges of your pool. They cling to the floor and walls thanks to vacuum and water pressure. To understand how this happens, let's take a look at how a liner is installed:

  1. First, the liner is dropped into an empty pool over a sand (or other) base and preliminarily stretched to cover the interior of the pool. The top and only the top of the liner is secured by plastic coping, while the rest hangs semi-loose.
  2. Wrinkles in the liner are smoothed out and the pool begins to be filled with water.
  3. As the pool continues to be filled, a vacuum is connected to suck the air out from between the liner and the pool walls.
  4. Once the air is gone and all the water is in, the liner is installed!

It's important to never pump all the water out of a lined pool (even for winter) because relieving the pressure on the liner will cause it to stop clinging to the walls. Liners can withstand winter temperatures and ice just fine, so you just have to seal the piping and make sure there's no water in it, but the pool can stay filled.