Calcium Phosphate

The Mystery of the 'Wet Cornflakes' in Your Pool

If you've ever found strange, white, flaky substances floating in your pool that look suspiciously like soggy cereal, you're not alone. This mysterious phenomenon has puzzled pool owners and professionals for years, and it's more common than you might think. What you're seeing is likely calcium phosphate precipitation – a chemical reaction that creates one of the most peculiar-looking pool problems you'll ever encounter.

As Wayne from the Talking Pools Podcast explains:

People were calling me when I used to do tech calls, but they were getting stuff in their pools coming out of the return lines that they didn't recognize. And one of the things was it looked like wet corn flakes is the way somebody describes it to me one time. You know, you sit in the bowl for too long and the milk's been sitting there and whatnot. But the guy described it as white, wet corn flakes.

— Wayne, Talking Pools Podcast

Understanding calcium phosphate formation is crucial for pool maintenance, especially as phosphate levels in municipal water supplies continue to rise and saltwater pools become increasingly popular.

Understanding the Perfect Storm: Four Conditions for Calcium Phosphate Formation

Calcium phosphate doesn't just appear randomly in your pool. It requires what experts call a 'perfect storm' of conditions to form. These four factors must align for you to see those infamous wet cornflake formations:

• Elevated Water Temperature: Your pool water needs to be warmer than normal, typically exceeding 84-85°F
• Measurable Phosphate Levels: Phosphates must be present at levels over 125 parts per billion
• High Calcium Hardness: Calcium levels generally need to exceed 500 parts per million
• Elevated pH: Your pH must be on the high side, typically 7.6 or higher

When these conditions converge, they create an ionic attraction between the phosphate (PO4) and calcium molecules, forming the calcium phosphate precipitate that manifests as those strange, flaky deposits.

Why Saltwater Pools Are Particularly Susceptible

Saltwater pool owners face a unique challenge when it comes to calcium phosphate formation. The salt cell generators that make these systems possible also create conditions that favor precipitation.

Steve shares his experience with this issue:

We have in fact, but it's more of a problem with us with our saltwater pools. And the reason being is because saltwater pools here on the West Coast are pretty prominent. I wouldn't say that all of my clients have it, but over 50% for sure. So with that, we were having these issues where we were getting this weird white stuff that was on the bottom of the pool.

— Steve, Talking Pools Podcast

The challenge with saltwater systems is that they naturally push pH levels higher, creating one of the key conditions needed for calcium phosphate formation. Pool professionals constantly battle high pH in these systems, requiring regular additions of muriatic acid to maintain proper balance.

Additionally, the calcium phosphate buildup doesn't just affect the pool water – it can coat the salt cell itself, reducing its efficiency and potentially leading to premature equipment failure.

The Hidden Phosphate Problem in Municipal Water

One of the most frustrating aspects of dealing with phosphates is that they're increasingly present in municipal water supplies. Water treatment facilities add phosphates as orthophosphates to help control corrosion in aging pipe systems.

Steve encountered this problem firsthand:

So it's far off that the phosphates here aren't a little bit. It winds up that it's I've seen it coming out of the top at like fifty seven hundred seventy five hundred. So much so where I called the EPA and I called the township and I was like, what, you know, in this in that specific city, I think it was so like that we were in and I was like, Hey, like what's going on?

— Steve, Talking Pools Podcast

When phosphate levels in tap water reach these extreme levels (5,700-7,500 parts per billion), traditional treatment methods become nearly impossible. Every time you add fresh water to the pool, you're introducing more phosphates, creating a cycle that's difficult to break.

The EPA recommends that phosphate levels in municipal water should be less than 200 parts per billion, but treatment facilities sometimes exceed this temporarily when applying corrosion control treatments like zinc orthophosphate.

Identification and Testing Challenges

One of the most important things to understand about calcium phosphate is that there's no direct test for it. You can't simply dip a test strip and get a 'calcium phosphate level' reading.

There is no test for calcium phosphate doesn't exist.

— Wayne, Talking Pools Podcast

Instead, pool professionals must test for the individual components – calcium hardness and phosphate levels – and look for the visual signs. The substance can appear in several forms:

• White, flaky deposits that resemble wet cornflakes
• Crusty white coating on pool surfaces
• Buildup on salt cell plates
• Fine white powder settling on the pool bottom

The challenge is distinguishing calcium phosphate from other similar-looking substances like calcium carbonate scale or even undissolved salt in saltwater pools. This requires experience and understanding of your pool's specific conditions.

Practical Solutions and Prevention Strategies

Addressing calcium phosphate requires a multi-pronged approach targeting each of the contributing factors:

pH Management: Keep your pH levels between 7.2-7.6. For saltwater pool owners, this means being more aggressive with acid additions and potentially using automated pH controllers.

Phosphate Removal: Use phosphate removers, but be strategic about application. Steve recommends using tablet forms in skimmer socks to avoid creating additional problems:

Calcium Hardness Control: If your calcium levels are consistently above 500 ppm, consider partial drain and refill with softer water, or use sequestering agents to keep calcium in solution.

Temperature Management: While you can't always control water temperature, be extra vigilant during hot summer months when conditions favor precipitation.

Water Source Alternatives: When dealing with high-phosphate municipal water, consider alternative water sources for top-offs, or install whole-house water treatment systems.

The Bigger Picture: Modern Pool Chemistry Challenges

The calcium phosphate issue represents a broader challenge in modern pool maintenance. As municipal water quality changes and new pool technologies emerge, pool professionals must adapt their approaches.

The rise in phosphate levels isn't just a locational problem – it's becoming more widespread as aging infrastructure requires more aggressive corrosion control measures. This means calcium phosphate formation may become an increasingly common issue for pool owners nationwide.

Understanding the science behind these formations empowers both pool professionals and owners to take proactive measures rather than simply reacting when problems appear.

Conclusion: Knowledge Is Your Best Defense

Calcium phosphate formation might look mysterious, but it follows predictable chemical principles. By understanding the four conditions that create the perfect storm – elevated temperature, phosphate presence, high calcium hardness, and elevated pH – you can take targeted action to prevent or address the problem.

Remember that there's no single 'magic bullet' solution. Success requires a comprehensive approach that addresses each contributing factor. For saltwater pool owners, this means being especially vigilant about pH control and regular equipment maintenance.

Most importantly, don't assume your pool chemistry is fine just because the water looks clear. As the experts remind us, proper testing and proactive management are essential for preventing these and other pool chemistry issues before they become major problems.

Episode Chapters

• 00:00 Introduction to Calcium Phosphate
• 05:00 Saltwater Pool Challenges
• 12:00 Phosphate Sources and Municipal Water Issues
• 18:00 Testing and Identification
• 25:00 Treatment Solutions
• 32:00 Prevention Strategies