Fiberglass pools generally are easier and cheaper to maintain than other types of pools. They rarely suffer from stains when properly maintained and managed, and they need fewer chemicals and lower amounts of electricity to keep it that way. Another attraction of fiberglass pools is that they have smooth surfaces that won't cut or scratch swimmers.
Discoloration similar to bathroom rings, however, can appear on the waterline because of suntan creams, body oils, and metals in the pool chemicals. Rust can also build up in a fiberglass pool, caused by chemicals and mineral deposits. Rust stains are a bit trickier, but with the right tools and equipment can be removed easily. Your owner's manual should have instructions or tips for getting rid of both of these blemishes, but if it doesn't—or you've lost the manual—you can call your manufacturer directly or follow the general solutions below!
Step 1 - Remove Light Bathroom Ring Stains
Commercial products like Off the Wall, Jack's Magic Blue Stuff, and pool tile cleaners can get rid of light bathroom rings found around the pool. You can also apply vinyl cleaner or a non-abrasive tile cleaner not originally designed for pool use. Be careful with these and make sure to test them in an inconspicuous area first just in case they have a damaging effect on your fiberglass.
Another way of removing light stains is to scrub the affected area with a sponge, soap, and warm water. You can also use liquid dish detergent as an alternative to soap. Whichever you choose, rinse the area thoroughly afterward so you do not end up with suds in your pool water.
Step 2 - Remove Heavy Bathroom Ring Stains
While wearing gloves, pour oxalic acid in the water to remove heavy bathroom ring stains. The water may appear cloudy for a few days following treatment, but you can run the pool filter to clear it before you pour chlorine. Follow manufacturer's specifications as to the proper amount of chlorine for your size pool. Also, make sure that the pH balance of the water is 7.5 when the pool filter is in use.
A Mr. Clean Magic Eraser is another effective product for heavy ring stains. Scrub the affected area until it clears up. The solution in the eraser is gentle and will not damage the surface. However, do not use commercial abrasive brushes or cleaners when removing these stains, as they may damage your pool.
Step 3 - Remove Rust Stains
For rust, apply a Vitamin C tablet directly to the stain until it clears up. If it is caused by metal, it will normally dissolve quickly, but you can use a soft-bristled brush to remove any excess rust.
When you have rust infection spread out across the pool, put ascorbic acid powder to your pool filter. Follow manufacturer's specification for optimum results.
Another way of dissolving rust is to rub chlorine tablets on the affected areas. Try your soft-bristled brush again on any stubborn and excess stains.
Step 4 - Stain and Rust Prevention
To prevent future blemishes on your fiberglass pool, remove all foreign metal objects from the water. Always follow your manufacturer's specifications when adding or putting chemicals in the water, and add metal treatment whenever you're adding water to the pool. Regularly check your pool's pH as well, to keep it at ideal levels.
Pool stains need to be cleared right away, because they become stubborn and hard to remove when left unattended for a long time. It's recommended that you use household products first such as soap and water when removing stains, as they contain light chemicals that are kind to pool surfaces. Only proceed to other solutions when the easiest prove ineffective.