Proper use of chemicals and regular monitoring of your water will help reduce chemical damage, metal stains and algae growth. But you will still need to clean your vinyl pool liner on a regular basis to keep it looking its best. Regular cleaning will keep dirt to a minimum, though you may still need to do some heavy-duty cleaning once or twice a season. With the right cleaning methods, your vinyl pool liner will look good for years to come.
Use a nylon pool brush to scrub down your entire liner on a weekly basis throughout the swimming season. A brush without any sharp edges is best, such as the deluxe wall brush available from Save on Pool Supplies. A liner is susceptible to tearing, so sharp edges can easily cause damage.
Apply a mild cleanser directly to dirt on your vinyl liner, or rub it on with a soft cloth. You can use a regular vinyl cleaner like Armor All Cleaner, or you can buy a specialty cleaner like Bio-Dex Quick 'n Thick.
Get ascorbic acid, or Vitamin C, to help you get rid of stubborn stains, which are likely metal stains. You can use Vitamin C tablets intended for ingestion, or you can get granular ascorbic acid intended for use in pools and water features, such as Vita-D-Chlor. Simply rub the ascorbic acid onto the stain and you should see an immediate effect.
Check the water line regularly for build up, which can eventually build up enough to collect dirt and to stain your vinyl liner with metal stains. Rubbing the waterline with a pool scrubbing mitt, like that you can get from In the Swim, makes this maintenance easy to perform. Add a small amount of cleaner or ascorbic acid if you need to.