Brown and sticky substances, otherwise known as swimming pool liner tar can occur, staining pool liners as a result of poor maintenance. The following is a description of how this phenomenon usually happens:
Swimming pools that are not properly maintained with chemicals all become infested with
green algae at some point. When this happens it is obviously a sign to get the swimming pool back into shape. The first and most common step to combat green algae formation is to add chlorine and algaecide to the swimming pool. Depending on how dense the algae formation is, it usually is killed and falls to the bottom of the pool. Pool liners can easily pick up the dead algae in the form of a brown stain. The longer this brown, sticky substance remains on the vinyl pool liner, the more likely it will become a more permanent stain. However, it seems to remove itself over time with
proper chemical maintenance.
This type of stain also seems to occur, or more appropriately become discovered when the swimming pools are opened in the spring time. This is probably due to the fact that most Closing (Chemical) kits for pool liners contain chlorine and algaecide.
To avoid this brown stain or tar, never fall back on the chemical maintenance, but if you do, then vacuum the dead algae debris as quick as you can. Remember to avoid being abrasive with the liner. Scrubbing the liner only does more damage to vinyl pool liners. If a stain cannot be removed through vacuuming, then just let it remain for some time to see if the chemicals will gradually remove the problem. If the stain remains throughout a long period of time (1 year or more), and the color of the stain resembles a black color, then your problem may be due to
black algae and you will generally be stuck with it until you replace the pool liner.