If you own a fiberglass pool you will need to read this post on fiberglass pool stain removal & prevention. Most fiberglass pool owners think that their pool cannot stain. Unfortunately, fiberglass pools can stain but you can easily remove the stain and prevent it from happening again. Of course, it’s always better to prevent the stain forming in the first place than trying to remove a stubborn stain later.
First of all before you can remove a stain you need to identify what caused the stain. Many stains are simply caused by decomposing organic material such as insects, flowers, leaves, seeds and berries that have sunk to the bottom. These organic stains are usually green or brown in appearance.
Some pool stains are caused by dissolved metal ions in the water.
Other stains can be the beginning of green or black algae growing in the pool.
If you have stains caused by dissolved metal ions in the water, please refer to our article:
How to Clean Metal Stains from a Pool
Table of Contents
Fiberglass Pool Stain Removal
Fiberglass pool surfaces are very popular because they look great and have many advantages:
- non-porous (chemicals and contaminants cannot penetrate the surface)
- long-lasting
- less maintenance
- easy to clean
- does not become etched or rough
- smooth surface so that you don’t injure yourself
- less susceptible to algae growth
- less expensive than other surface finishes
However, all pools can develop stains.
The most common stain in a fiberglass pool is a light stain around the waterline of the pool. This stain is similar to a bathtub ring caused by dirty, soapy water. However, your nice pool does not have dirty, soapy water so how does this happen?
Fiberglass pool stain removal can be challenging as most fiberglass pools do not have a tile band at the waterline, like a concrete and plaster pool. The tile band is installed to protect the plaster pool surface at the waterline. The tiles are tough and are scrubbed clean with a stiff wire brush to remove algae, dirt and other scum. You cannot scrub a fiberglass pool with a wire brush! So it is better to prevent the waterline ring form forming in the first place.
How to Remove Waterline Stains in a Pool
A waterline ring on the pool surface can be removed with several cleaning products.
“Clean and Perfect” is an enzyme-based cleaner that works well to remove waterline rings.
“Pool Magic” will remove excess oil from the pool.
“Stain Free” is a natural product, containing vitamin C product (ascorbic acid), that gently cleans fiberglass pool surfaces.
“Metal Eliminator” products are useful to add an element of protection to your pool against metal ions accumulating in the water.
How to Prevent Organic Stains in a Pool
Preventing organic stains from forming in your pool is easy.
- Keep the correct level of sanitizer (chlorine, bromine, etc.) to kill bacteria and algae before it can multiply in the pool.
Please read: How to Balance the Pool Water
- Ensure the water chemistry (especially pH and total alkalinity) are in the normal ranges for your pool all the time.
- Use a pool cover to keep organic material out of your pool.
- Use a skim net to remove organic material floating in the pool before it sinks to the bottom and decomposes.
Please read: How to Remove Pollen from a Pool
- Run your pump long enough each day to remove organic matter from the surface and trap it in the skimmer basket. We recommend a variable speed pool pump running at lower rpm for a longer period of time. These pumps actually save you money as they use much less electricity compared to old-style single speed pumps.
- Regularly vacuum the bottom of the pool to remove sunken organic material.
- Install an automatic pool cleaner to keep the bottom free of organic material.
- Unfortunately swimmers coated in oily sunscreen (or baby oil) will introduce oil to the pool. The excess oil floats on the surface and can stain the waterline. The filtration system cannot remove oil from the water. Try using non-oil-based sunscreens.
How to Prevent Metal Stains in a Pool
- Always maintain your pool chemistry and test the water every week.
Please read: How to Test Pool Water
- Avoid filling the pool with water containing metal ions. Always test the water source first for metals. Do not use water from bores, streams and dams. Rainwater captured from your roof is usually ok but have it tested to make sure.
- Drain and refill your pool water every 5 years to eliminate total dissolved solids. This is the only way to guarantee your pool water is fresh and free from dissolved solids. There are no chemicals you can add to a pool to remove dissolved solids.
- Add a metal sequestering chemical to the water to prevent the staining problem recurring.
- Check your water heater for metal corrosion which will leach copper and iron into the pool water. There may also be accumulated calcium scale in the heater.
- Check your filtration system for metal parts that are showing signs of corrosion. Most systems are manufactured with PVC plumbing which cannot corrode but there may be a small metal part that has corroded. If so replace it with a new fitting.
- Check your chlorinator cell for corrosion on the electrodes. Acid wash these cells to remove corrosion and scale. Replace your chlorinator cell when required as per the manufacturer’s specifications.
Conclusion
Fiberglass pool stain removal and prevention is easy when you follow our recommendations above.
If you have any other pool maintenance questions, please use the search box at the top of the page to find the answers.