Measuring Chemicals: Volume vs. Weight

If you've ever grabbed the wrong measuring cup to dose your pool chemicals, you might have unknowingly been wasting money and compromising your water quality. This seemingly simple mistake is costing pool professionals and homeowners more than they realize, and it's one of those "small" details that can add up to significant problems over time.

In a recent episode of the Rule Your Pool podcast, host Eric Knight and co-host Jared dive into why understanding the difference between volume and weight measurements isn't just chemistry class theory—it's practical knowledge that can save you money and prevent dangerous chemical reactions.

The Three Most Profitable Tools Every Pool Pro Should Use

Before diving into the measuring discussion, Knight emphasizes three essential tools that most pool professionals overlook, despite their low cost and high impact on profitability:

• A clean white bucket (not orange or blue) for pre-dissolving dry chemicals and seeing color contrast
• A thermometer for accurate LSI calculations
• Proper measuring cups for both liquid and dry chemicals

These three tools are a clean white bucket, a thermometer, and measuring cups... they are gonna be used to pre-dissolve dry chemicals, to dilute acid, and the reason it needs to be white is to see color contrast in water if you're doing something like the white bucket test.

— Eric Knight, Rule Your Pool Podcast

The white bucket specifically allows you to observe color changes and reactions that might be invisible in colored containers—a crucial safety feature when working with reactive pool chemicals.

Why Liquids and Solids Require Different Measuring Approaches

The fundamental difference between measuring liquids and dry chemicals comes down to basic physics. Liquids conform perfectly to their containers, while dry chemicals contain air pockets that create volume variations.

The real reason is when something is liquid, it will fill the exact volume of whatever container you put in it. That is not necessarily the case of dry stuff. So if you have flakes, for instance, there's gonna be a higher volume. It's gonna look like a bigger pile because there's a lot of air pockets in it.

— Eric Knight, Rule Your Pool Podcast

Consider diatomaceous earth (DE) versus calcium hypochlorite (cal-hypo). One pound of DE appears as a much larger, fluffier pile compared to one pound of cal-hypo, which looks more compact and dense. If you're measuring by volume instead of weight, you could be dramatically under-dosing or over-dosing your pool.

This is why the Arenda calculator specifically notes that "dry chemicals are by weight, liquids are by volume"—a distinction that many pool professionals miss in their daily operations.

The Hidden Costs of Improper Chemical Measuring

Using the wrong measuring method doesn't just affect chemical efficacy—it directly impacts your bottom line. When Jared discusses chemical strength variations, he highlights a concerning industry practice:

There's percentage strengths of Calhypo that range from 48% to 73%. That is a massive difference... if you normally buy 73% Calhypo and they give you 68% Calhypo. That is over a 7% difference in strength. So therefore you're paying 7% more.

— Jared, Rule Your Pool Podcast

This cost increase compounds when you factor in:

• Increased calcium levels from using more cal-hypo
• Higher salt content from additional chlorides
• More frequent chemical additions
• Potential water balance issues requiring correction

For pool service professionals managing dozens of accounts, these "small" percentage differences can translate to hundreds or thousands of dollars in unnecessary chemical costs annually.

The Right Tools for the Job: Liquid vs. Dry Measuring Equipment

Professional pool chemical measuring requires two distinct types of measuring tools. Standard kitchen measuring cups won't cut it for professional pool maintenance.

For Dry Chemicals: Use scoops with graduated lines specific to different chemical types. These specialized scoops account for the density differences between chemicals like:

• Sodium bicarbonate
• Calcium hypochlorite
• Calcium chloride
• Diatomaceous earth

You want one that has a line for sodium bicarb, for Calhypo, calcium chloride, et cetera. DE if that's the case. And you should be able to use that and just make sure that the chemicals don't interact.

— Eric Knight, Rule Your Pool Podcast

For Liquid Chemicals: Use standard volume measuring cups, but ensure they're dedicated to chemical use and properly cleaned between different products.

Critical Safety Considerations When Measuring Pool Chemicals

The podcast hosts emphasize that proper measuring isn't just about accuracy—it's about preventing dangerous chemical reactions. Cross-contamination between measuring tools can lead to serious safety hazards.

A recent customer incident illustrates this danger: residual cal-hypo on a wet measuring cup mixed with dichlor, causing an explosive reaction that destroyed the customer's chemical cart.

You should never just transfer this stuff without rinsing the thing off and drying it first. You do not wanna have residual Calhypo stuck to a wet cup and then go reach in and scoop granular trichlor.

— Eric Knight, Rule Your Pool Podcast

Safety protocols for chemical measuring include:

• Thoroughly clean and dry measuring tools between different chemicals
• Use dedicated scoops for specific chemicals when possible
• Never put wet measuring tools into dry chemicals
• Label measuring tools to prevent cross-contamination
• Keep multiple measuring tools to avoid mixing reactive chemicals

Practical Implementation: Making Accurate Measuring Part of Your Routine

Implementing proper measuring techniques doesn't require a significant investment, but it does require changing established habits. Here's how to make the transition:

For Pool Professionals:

• Invest in graduated chemical scoops available at pool supply stores
• Create a dedicated measuring station in your service vehicle
• Use the Arenda app's Chemiculator feature to input custom chemical percentages
• Train staff on the weight vs. volume distinction
• Establish cleaning protocols for measuring equipment

For Homeowners:

• Purchase separate measuring tools for pool chemicals
• Never use kitchen measuring cups for pool chemicals
• Follow manufacturer dosing instructions based on weight, not scoops
• Consider investing in a small digital scale for precise measurements

The new Chemiculator feature in the Arenda app allows users to input custom chemical percentages, providing real-time calculations of chemical impacts on water chemistry. This tool helps users see exactly how different chemical strengths affect their specific pool conditions.

Conclusion: Small Changes, Big Results

The difference between volume and weight measuring might seem like a minor technical detail, but as Eric Knight and Jared demonstrate, these "small" details add up to significant impacts on both safety and profitability. Whether you're a pool professional managing multiple accounts or a homeowner maintaining your backyard oasis, using the right measuring tools and techniques is one of the most cost-effective improvements you can make.

By investing in proper liquid and dry measuring equipment, understanding chemical density differences, and maintaining strict safety protocols, you'll not only save money on chemical costs but also achieve more consistent water quality results. As the podcast hosts emphasize, these aren't expensive solutions—they're fundamental practices that separate professional pool maintenance from guesswork.

Remember: one pound is one pound, regardless of how much space it takes up in your measuring cup. Master this concept, and you'll be well on your way to ruling your pool with both precision and profitability.

Episode Chapters

• 00:00 Introduction and Welcome Back
• 03:30 The Three Most Profitable Pool Tools
• 06:45 Why Volume vs Weight Matters
• 09:15 Chemical Density Differences Explained
• 12:00 Safety Considerations and Cross-Contamination
• 15:30 Chemical Strength Variations and Cost Impact
• 18:45 Practical Implementation Tips