Scale and Scum Lines on Pool Furniture (w/ Mike Collins, TenJam)

If you've ever owned pool furniture that sits partially submerged in your swimming pool, you've probably noticed those unsightly white calcium deposits and grimy scum lines that seem to appear right at the waterline. What starts as pristine furniture quickly develops these stubborn marks that resist normal cleaning efforts, leaving pool owners frustrated and searching for answers.

In a recent episode of the Rule Your Pool podcast, host Eric Knight sat down with Mike Collins from TenJam, a Minnesota-based pool furniture manufacturer, to dive deep into this common problem. What they discovered reveals fascinating insights about water chemistry, temperature effects, and why your pool furniture might be acting like a calcium magnet.

Understanding Pool Furniture Manufacturing and UV Protection

Before diving into the calcium problem, it's important to understand what makes quality pool furniture different from cheap plastic toys. TenJam specializes in rotational molding (roto molding) and pivoted to pool furniture manufacturing during COVID-19 when schools shut down and their educational furniture business was impacted.

A lot of that does come down to just the slower manufacturing process. But when we do have this plastic material, polyethylene is what we use. We do have additives in it. And we have to use the highest grade of UV color stabilizer as an additive in these products.

— Mike Collins, Rule Your Pool Podcast

The quality of UV stabilizers directly impacts both cost and performance. While cheaper plastic furniture might cost $100, quality pool loungers can run $500-700 because they're designed to withstand constant sun exposure without becoming brittle or fading quickly. However, even the best UV stabilizers can't prevent all color fading over time—they just slow the process significantly.

The Engineering Challenge: Keeping Furniture Submerged

One of the most interesting aspects of in-pool furniture design is solving the buoyancy problem. Hollow plastic furniture naturally wants to float, so manufacturers have developed several creative solutions:

Drainage Method: Some furniture uses holes in the bottom and top to allow water to flow through, relying on the plastic above the waterline to provide weight.

Water Trapping Method: Other manufacturers use screw plugs that allow you to fill the furniture with water, then seal it to create weight.

TenJam's Patented Approach: Their Shays lounger uses a one-way air valve system that allows water to enter and circulate while preventing stagnation.

At 10 Jam, we never have the method that holds the water inside. So we want to get away from that because we like the idea of the water being able to constantly move through the core of the product to refresh itself.

— Mike Collins, Rule Your Pool Podcast

The circulation aspect is crucial because stagnant water inside furniture can become a breeding ground for algae and bacteria, especially when heated by the sun.

The Science Behind Scale Formation on Pool Furniture

The real revelation in this podcast comes when Eric Knight explains why pool furniture seems particularly susceptible to calcium deposits and scum lines. The answer lies in basic chemistry and physics.

Pool furniture experiences what Knight calls "the peanut butter and jelly effect"—a combination of organic scum and mineral scale. Oils and organics naturally float and stick to surfaces at the waterline, while calcium scale forms when water becomes oversaturated and needs to precipitate calcium carbonate.

Think about your shower at home. Why is it that the shower head can have calcium scale on it, but the tub doesn't? It's temperature. It's hotter there... if you have hard water, you're going to see it on the shower head first. And that's because the temperature is so much higher there, which means the LSI is higher.

— Eric Knight, Rule Your Pool Podcast

The Langelier Saturation Index (LSI) is the key measurement here. When water is oversaturated with calcium (high LSI), it must precipitate calcium somewhere to return to its natural balanced state. Higher temperatures increase the LSI, making scale formation more likely.

Pool furniture sitting in direct sunlight all day becomes significantly hotter than pool tiles or other surfaces. This temperature differential creates the perfect conditions for calcium precipitation, explaining why furniture often shows scale before other pool surfaces do.

Geographic Patterns and Seasonal Trends

Collins noticed interesting patterns in customer complaints about scale and scum formation:

These questions first arise in our Arizona areas and Southern California areas. And then as the season progresses, it becomes more like everywhere. And then now it's kind of coming back to where it's like, are people back in Arizona, Southern California is where the questions are coming from right now.

— Mike Collins, Rule Your Pool Podcast

This pattern makes perfect sense from a chemistry standpoint. Arizona and Southern California have several factors working against them:

• Higher ambient temperatures
• More intense UV radiation
• Often harder water with higher calcium levels
• Year-round pool usage
• More evaporation leading to concentrated minerals

As summer progresses, pools everywhere begin experiencing similar conditions—higher temperatures, more UV exposure, and increased evaporation—leading to scale problems spreading to other regions.

The Hidden Problem: Interior Scale Formation

While Collins hadn't observed scale formation inside furniture pieces, Knight's explanation suggests this could be an even bigger problem for furniture that traps water internally:

Water trapped inside plastic furniture experiences even higher temperatures than the exterior surfaces. Without circulation, this superheated water would create extreme LSI conditions, potentially leading to significant scale buildup inside the furniture where it can't be seen or easily cleaned.

This reinforces the value of TenJam's approach to allow water circulation rather than trapping it inside the furniture.

Practical Solutions for Pool Owners

Understanding the chemistry behind scale formation leads to several practical strategies:

Water Chemistry Management:

• Regularly test and balance your pool's LSI using tools like the Orenda Calculator
• Maintain proper calcium hardness levels for your climate
• Don't let your pool become oversaturated with calcium

Furniture Selection:

• Choose furniture that allows water circulation rather than trapping it
• Look for quality UV stabilizers even if the initial cost is higher
• Consider furniture placement to minimize direct sun exposure when possible

Maintenance Strategies:

• Regular cleaning of waterline areas before deposits become established
• Remove furniture periodically to clean thoroughly
• Address water chemistry issues promptly rather than relying solely on cleaning

Regional Considerations:

• Pool owners in hot, sunny climates should be especially vigilant about LSI balance
• Consider more frequent water testing during peak summer months
• Plan for more aggressive maintenance schedules in high-risk areas

The Bigger Picture: Chemistry Trumps Cleaning

Perhaps the most important takeaway from this podcast is Collins' realization that water chemistry is foundational to solving furniture maintenance problems:

"So no matter what kind of power washing and different things we're trying to tell people to use, a lot of it really comes down to the foundation of the water chemistry. And I never knew that."

This insight applies beyond just pool furniture. Many pool maintenance problems that seem like cleaning issues are actually chemistry problems in disguise. By addressing the root cause—water balance—pool owners can prevent problems rather than constantly fighting symptoms.

The collaboration between furniture manufacturers like TenJam and water chemistry experts like Orenda represents exactly the kind of cross-industry knowledge sharing that benefits pool owners. When manufacturers understand the chemistry behind the problems their customers face, they can design better products and provide more effective guidance.

For pool owners dealing with scale and scum on furniture, the message is clear: start with your water chemistry, choose quality furniture designed for circulation rather than water trapping, and understand that prevention through proper water balance is far more effective than trying to clean problems after they've developed. Your pool furniture—and your back—will thank you for it.

Episode Chapters

• 00:00 Introduction and Guest Background
• 05:00 TenJam's Manufacturing Process and UV Protection
• 10:00 Engineering Solutions for Buoyancy Control
• 15:00 Customer Problems with Scale and Scum Lines
• 20:00 The Science Behind Scale Formation
• 25:00 Geographic Patterns and Seasonal Trends
• 30:00 Temperature Effects and LSI Violations
• 35:00 Practical Solutions and Prevention Strategies