Clean an acrylic bathtub liner using mild dish washing soap and water. If hard water scale builds up on the liner, use a dilute solution of vinegar and water. A solution of bleach and water provides an effective disinfectant if the liner requires it. Avoid the use of any abrasive cleaner, even those the manufacturer labels as soft, due to their potential to scratch the acrylic.
Some cleaners recommended for plastic or acrylic showers are not appropriate for use on the liner. These products include Lysol disinfecting cleaner, ammonia and some glass cleaners. These stronger cleaners cause the liner to crack in a characteristic pattern. Such cracking from the use of the chemicals voids the liner warranty.
If the drain is plugged, try removing the stopper and fishing out any hair that the cross members in the drain tend to catch. If you must use a drain cleaner to clear the tub drain, choose a liquid version, and pour it into the drain with a funnel. Bail out any standing water from the tub before adding the drain cleaner.
Acrylic bathtub liners bring new life to old bath tubs. Manufacturers design the liners for exact fits for many different models of tubs. If you use a cleaner other than the ones the manufacturer recommends, test it in an inconspicuous spot before applying it to the rest of the liner.