Vinyl-liner pool
Also called: vinyl pool, liner pool.
A vinyl-liner pool is an in-ground pool built from steel or polymer wall panels set on a footing, with a custom vinyl liner, typically 20–30 mil, fitted inside to hold the water. It is the least expensive in-ground type, but the liner is a consumable replaced every 7–10 years.
Why it matters
The surface is smooth, soft and algae-resistant, and the liner is inert, so it does not raise pH the way plaster does. Protect it: no wire or stiff brushes, vinyl-safe robots only, and watch for punctures. Liners are sensitive to low pH, below about 7.0, which leaches the plasticizers and makes the vinyl brittle. Never fully drain one in Florida, because a drained liner can float off the walls. For a salt pool, use polymer wall panels, not galvanized steel. Manufacturer warranties of 20–25 years are prorated and cover defects, not fade or wear. Above-ground pools hold their water in a vinyl liner too.
In numbers
Thicker 27–28 mil liners last longer than thin 20 mil ones.