If your pool liner has torn like in the picture to the left it is definitely time for a pool liner replacement. This means that your pool liner is very brittle and your pool is in need of makeover. If your pool liner is 20 years old then you are doing well and it is definitely time for a new liner. If your liner is 10 years or younger there is a very good chance that your pool liner could have lasted longer with more attentiveness to chemical balancing.
Over dosing on chlorine frequently accelerates the liners ageing. Sun damage around your pool water line is also a contributing factor. The sun bakes on dirt, scum, and organic matter on to your pool liner which actually dries your liner out over time. This problem is best alleviated by cleaning above the waterline with a vinyl liner cleaner.
Liner Repair: If your pool liner is in decent condition and is not old, then there is a good chance that it can be repaired.