Fiberglass pool stain remover

In most cases, our fiberglass pool stain remover kit completely clears white calcium formation.  It also restores the smooth blue finish and has prevention products to help keep it looking good. However, if left untreated, this white build-up will spread across the pool surface and become thicker and more noticeable over time.  For this reason, we strongly suggest doing something about it as soon as possible.  Our fiberglass pool stain remover compound removes calcium from fiberglass pools without draining.  It works by softening and dissolving the white calcium build-up without acid washing.

Whitening or discoloration on fiberglass pool surfaces is normally a result of one of the following factors. We have ranked them in order from most common (1) to least common (5):

  1. Calcium stain buildup on fiberglass surface.
  2. Pool interior is in final stages of aging (25+ years).
  3. Bleaching of color from gelcoat interior.
  4. The gelcoat layer has not been cured properly in the factory.
  5. Undissolved sodium bicarbonate has bonded to the pool surface.
Calcium on Fibreglass The Pool Stain Removers 1

These pictures show heavy calcium stain formation in need of our fiberglass stain remover.

Calcium on Fibreglass The Pool Stain Removers 2

Our fiberglass pool stain remover treatment without draining or acid washing.  Our customer was thrilled with the result.

1. Calcium build-up on the pool surface

High pH levels in the pool water may cause any calcium on fiberglass pools to precipitate onto the pool surfaces. When this happens, it often leaves a white gritty layer.  As the picture shows, this white layer becomes very noticeable if the pool water drops below its normal level.

To help prevent calcium, we suggest regularly testing the pH and calcium hardness levels in your pool water.  Remember, High calcium (above 350ppm) often occurs for two reasons.  First, too much calcium chloride (calcium increaser) has been added to the pool water. When this happens, it leads to calcium formation. Secondly, calcium-based granular chlorine will increase the calcium hardness levels in your pool. If your calcium levels are rising for no reason, then it is likely that granular chlorine (calcium hypochlorite) is the cause.

Ask your pool manufacturer before adding calcium

Before adding calcium to your pool water, contact your pool manufacturer (not your pool store) to find out what the calcium levels should be for your pool. This is because each fiberglass pool brand recommends different calcium levels.  Also, check that your pool store knows that your pool surface is fiberglass and not plaster.

As the pictures show, our treatments remove calcium from fiberglass pools without draining the pool water or acid washing.

Calcium on Fibreglass The Pool Stain Removers 5
This partially drained fiberglass pool shows the white calcium formation. Notice how thick and widespread it has become along the walls. This client did not attempt any type of treatment hoping that it would just disappear over time.

2. The pool interior is ageing

Fiberglass pools typically pass through two phases as the surface begins to age.  Firstly, the gelcoat blue color will slowly fade to white over time.  This fading happens because of chlorine in the water, years of sunlight and unbalanced water which all take their toll on the surface color. Remember, this color fading, which often starts after 15-20 years, is normal. This is not an indication of a faulty pool interior.

layers of gelcoat
This sectional diagram shows the layers of a fibreglass pool from top to bottom. Notice that the pool water can slowly circulate through the top surface layer of gelcoat. This process can allow the gelcoat to be effected by poor water chemistry.
gelcoat fading in fibreglass
Worn gelcoat in fibreglass pool

The second stage of ageing is when fiberglass pools (30+ years old) start to develop a persistent white powder that appears when the pool is brushed.  The powder is actually degrading gelcoat which has degraded over time.  This powder will eventually disappear in sections of the pool revealing the lower layers of fiberglass which are often dark brown. This breakdown is common in high friction areas such as steps and ledges. Remember, the best way to extend the life of your fiberglass pool is to maintain the water correctly.

3. Bleaching of fiberglass or gelcoat

Bleaching in a fiberglass pool happens when the pH and the chlorine levels are both very high at the same time. Remember, if the pool water remains unbalanced, it may start bleaching the surface.  Although fiberglass pools are required to resist bleaching due to mild water imbalance, they cannot withstand unbalanced water for very long so fading can occur.

Gelcoat bleaching from unbalanced water is often smooth and is non-responsive to cleaners and acids. In some cases, rubbing the surface with fine sandpaper can appear to remove this discoloration.  However, doing this will only remove the bleached gelcoat layer in your pool. Remember, sanding the gelcoat will leave your pool susceptible to future staining and reduce the life of your pool.  Do not sand your fiberglass with any type of abrasive as this may cause permanent damage and may void your pool warranty.

Careful with pool covers

Some pool owners feel that testing the water during winter (or when a pool cover is on) is not needed. Often, these same pool owners are horrified when they remove their pool cover and discover extensive surface bleaching. Remember, check your water during winter, even if the pool is covered.

Our treatments can sometimes help with surface bleaching.  However, there are cases where nothing can remove the visual effects of pool surface bleaching.  Please contact us for further information if you feel your pool may have this issue.

Gelcoat bleaching Fibreglass
Possible Gelcoat reaction with the pool water. Notice the smoothness of the white film and the distinct separation between the vivid blue and white along the waterline. Our treatments are sometimes effective with this issue.

4. Gelcoat not cured correctly during manufacture

In rare cases, the gel coat can discolor and remain white if it has not been cured properly during manufacturing.  So, if your pool has this issue, it will become obvious within the first few hours after the pool is filled with water. This discoloration occurs because the uncured surface is very porous.  Therefore, this allows the water to penetrate into the surface resin and bleach the pool surface.  In fact, this bleaching is permanent and cannot be fixed. Consequently, complete resurfacing of the fiberglass is required.

5. Adding undissolved sodium bicarbonate to the pool

If undissolved alkalinity increaser (sodium bicarbonate) is poured directly into the pool, it can cause a stubborn white film to appear on the pool surface. To avoid this, ensure that the buffer is dissolved in a bucket of water before it is added to the pool.  Remember, when buffer is first added to water it will start as milky white and then as it dissolves, the water will become completely clear. Finally, once the water is clear in the bucket then add it to the pool.

Do Not Drain or Acid Wash your Fiberglass Pool

DO NOT drain or acid wash your fiberglass pool – ever.  This is because very often the calcium on fiberglass pools is not removed.  However, if you insist on draining, we suggest using a licensed and insured professional. Remember, your pool walls must be properly cross-braced and secured to prevent buckling and cracking when your water is released.  Finally, if your empty pool and is forced upward through hydrostatic ground pressure, you’ll need the contractor’s insurance to pay for a new pool. Remember, you cannot simply push the pool back down if uplift occurs.

Pool walls buckle inward from ground pressure. Photo credit: APCO Pool Specialties
Pool walls buckle inward from ground pressure. Photo credit: APCO Pool Specialties
Swimming pool pushed upward while empty. Photo Credit: Pool Water Recycling
Swimming pool pushed upward while empty. Photo Credit: Pool Water Recycling

OPTION 1 – Calcium Removal DIY kit

What We Do 1


Calcium Stains in Swimming Pools The Pool Stain Removers 3


Calcium Stains in Swimming Pools The Pool Stain Removers 5



  • 1 bottle (64oz) of calcium dissolving and prevention formula
  • 7.7 lbs of our granular calcium stain dissolving compounds
  • Phone support from our technicians
  • Simple step-by-step instructions included
  • Pool does NOT need to be drained
  • Kit is shipped and tracked by FedEx
  • Kids are back in the pool in just 7 days
  • Kit is $295 for pools over 12,000 gallons


Enquire now!

OPTION 2 – Calcium Removal – On Site Technician


Calcium Stains in Swimming Pools The Pool Stain Removers 3


Calcium Stains in Swimming Pools The Pool Stain Removers 5



  • 64oz of our powerful calcium release and prevention formula
  • 7.7 lbs of our granular calcium dissolving compound made for your stain
  • Complete 7 point on site water testing
  • Your pool does NOT need to be drained
  • Kids are back in the pool in 7 days
  • Visit is $405 for pools 10,000+ gallons


Enquire now!

How fiberglass swimming pools are made

This short video shows the construction process followed to make a fiberglass pool shell. Notice how thin the topcoat is that is first sprayed onto the mold.  This sprayed surface becomes the inside of your pool when it is finished.  This is why it is important to maintain your pool water chemistry as this thin surface can be damaged.  The layers of fiberglass added throughout the process only exist to provide structural stability.