How to Fix Pool Plaster Discoloration

Pool plaster provides the backdrop for the water, giving your pool a specific aesthetic. That’s why the plaster color is chosen with a certain look in mind. If the color starts to change, you have to figure out the problem and fix it, so you can get the pool to its desired condition.

To fix pool plaster discoloration, you need to try an in-pool acid treatment or drain the pool and acid wash it (if in-pool treatment doesn’t work). If the problem is in the plaster content or application, you must replaster your pool to get back its desired look.

In this article, you will learn the exact steps you need to take to figure out the specific cause of pool plaster discoloration and adopt the best solution. More specifically, you will find out how to:

  1. Decide if the issue is in the pool plaster or the water chemistry 
  2. Find out if the damage can be fixed without draining the pool
  3. Fix the damage with an acid wash 
  4. Know if the damage has to be reversed with replastering
  5. Take preventive measures by avoiding water imbalance.

How To Fix Pool Plaster Discoloration: A Step-by-Step Look

Now that you know that it all starts with identifying a cause let’s look at each step more specifically. It will all lead up to an acid wash, an in-pool acid treatment, or replastering. And this section will explore how you can adopt the right solution.

Step 1: Identify the Cause

This is the first step in minimizing the effort required to fix pool plaster discoloration. The sooner you find the exact cause of the pool shade degradation, plaster darkening, or fading, the more reversible the damage will be. Since most causes have the same solution, you can afford to make the wrong conclusion and still end up with a better-looking pool.

That said, you cannot get the category of your plaster discoloration wrong. The causes can be broadly categorized as plaster-specific reasons and water chemistry reasons. Here are the different reasons your pool plaster color might be changing:

  • Calcium Chloride in the plaster mix (plaster-specific) 
  • Too much water in the trowelling stage (plaster-specific)
  • An extended delay in trowelling (plaster-specific)
  • Consistently high water pH (water chemistry)
  • Iron stains (water chemistry)
  • Bleaching from excess chlorine (water chemistry)

If the problem is plaster-specific, there is no way to bring the appearance of your pool to its intended best without replastering. Still, you can improve the plaster’s appearance to an extent.

Step 2: Assess the Extent of the Damage

Whenever the cause of pool plaster discoloration is off-balance or poor water chemistry, you can reverse the damage to a great extent. It is when the plastering practices or the plaster mix are at fault that you should not get your hopes up. Here are the different pool discoloration types alongside their chances of damage reversal.

White Spots or Greying White Plaster

These two are different manifestations of the same problem. When calcium chloride is used in the pool plaster mix, the white spots can develop upon filling the pool. Sometimes, late or harsh trowelling can also result in white spots. 

These can be removed with acid, but they keep coming back. In cases where the causes of white spots (trowelling delay, trowelling harshness, and calcium chloride content in the plaster mix) are compounded, you will notice greying of the plaster. This is far more evident in white plaster.

When trowelling harshness is the issue, the greying is uneven. When it is the delay and the calcium chloride that causes greying, the mottling is spread out. Either way, the damage is far from reversible, but acid washing can help.

Colored Plaster Starts Fading

If you have colored pool plaster and have noticed it starting to fade, you should jump with joy. This is by far the most reversible damage. You simply need to use in-pool acid treatment alongside plaster-brushing to get rid of it. 

The fading happens because a thin layer of calcium chloride deposits on the pool plaster. If the pool floor is relatively whiter than the walls, then the excess calcium hasn’t started sticking to the plaster. If the walls are also fading, then there is more serious scaling. In either case, acid is the answer.

White Plaster Starts Getting Brown

The advanced stage calcium scaling occurs with white plaster more often than with colored plaster. Because white deposits on a colored plaster can be easy to spot, they are often dealt with much earlier than when they surface on white plaster. 

So, does calcium get brown? No, but it attracts brown stains, which get baked into the layer. These stains can be removed with an acid wash, but the pool needs to be drained for the process.

Color Removed From Colored Plaster

This is tricky to assess because colored plaster can fade due to calcium deposits or because of chlorine bleaching the pool plaster. Either way, the effect is the same. So, when you assess the damage, you have to scrape a portion of the pool plaster and see if any white powder comes off. If it does, that’s calcium. But if the pool plaster is fading due to color loss, then you might have to freshen up the plaster.

Step 3: Check Whether In-pool Acid Wash Fixes the Discoloration

An in-pool acid treatment involves pouring the acid treatment into the pool and circulating the water until the thin films of deposits and stains get dissolved. This is fairly straightforward and requires less effort than draining.

Step 4: Drain the Pool and Acid-wash the Plaster

If the acid wash doesn’t work, then you need to get rid of the water and let the acid work on the plaster more directly. This solution is harsh on the plaster, which is why it should be used as the last resort to battle deposits and scaling.

Step 5: Replaster if Required

The previous step is the final step if acid washing can repair your pool plaster color. But if it can’t, then the issue might be in how the plaster is applied. If the damage to the plaster is irreversible, remember that the plaster’s adhesion to your pool is reversible. You can get the plaster removed and have a fresh layer applied by a better plastering company.

Final Thoughts

Pool plaster discoloration that occurs due to chlorine bleaching or poor plastering practices can be fixed with replastering. Almost all other sorts of discoloration can be fixed with an acid wash. Knowing the cause of your pool plaster fading, darkening, or staining is key to minimizing the effort you need to make.

Jed Arnold

Jed spent every year from the ages of 15 - 22 as a Lifeguard (Red Cross) and ages of 17 - 22 as a Certified Pool Operator (CPO). Between working for over a dozen facilities and owning a pool, he carries over a decade of pool experience.

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