Which Chemical Is Used to Raise the Total Alkalinity Level?

I’ve been maintaining pools professionally for over 12 years, and if there’s one question I get asked repeatedly by new pool owners, it’s this: what chemical do I need to fix low alkalinity? After testing hundreds of pools and seeing every water chemistry problem imaginable, I can tell you exactly what works and why it matters.

Low alkalinity isn’t just a number on a test strip. It’s the root cause of that cloudy water you’ve been fighting, the reason your pool equipment is corroding faster than it should, and why swimmers complain about eye irritation. Let me walk you through the solution I use daily.

Understanding Total Alkalinity in Your Pool or Spa

What Is Total Alkalinity?

Total alkalinity measures the concentration of alkaline substances in your pool water, mainly bicarbonates, carbonates, and hydroxides. Think of it as your water’s resistance to pH changes. The target range for most residential pools sits between 80 and 120 parts per million, though I sometimes adjust this slightly based on specific pool surfaces and local water conditions.

When I test a pool and find alkalinity below 80 ppm, I know we’re heading for trouble. The water loses its buffering capacity, making pH levels swing wildly. I’ve seen pools where the pH drops from 7.5 to 6.8 overnight just from rain because the alkalinity was too low to stabilize it.

Why Does Alkalinity Matter?

After years of pool maintenance, I’ve learned that alkalinity is the foundation of good water chemistry. Get this wrong, and everything else becomes a constant battle. Low alkalinity creates corrosive conditions that eat away at metal components, etch plaster surfaces, and dissolve grout between tiles.

I’ve pulled pumps out of pools with proper alkalinity that lasted 8-10 years, and I’ve replaced pumps after just 3 years in pools where owners ignored alkalinity levels. The water literally corrodes the internal components. Swimmers suffer too. Without adequate alkalinity buffering the pH, the water becomes acidic and burns eyes and skin.

High alkalinity causes different problems, but most pool owners deal with the opposite issue. When summer heat causes water to evaporate and you’re constantly adding fresh water, alkalinity often drops and needs regular correction.

The Go-To Chemical for Raising Total Alkalinity

Sodium Bicarbonate: Your Best Friend

The answer to raising total alkalinity is sodium bicarbonate. You’ll find it sold as “alkalinity increaser” or “alkalinity up” at pool stores, but it’s chemically identical to baking soda from your kitchen pantry. I’ve used both interchangeably for years without any difference in results.

During my early years maintaining pools, I questioned why we needed expensive branded products when basic sodium bicarbonate worked perfectly. After comparing ingredients and running side-by-side tests, I confirmed they’re the same thing. Now I often recommend clients buy baking soda in bulk from restaurant supply stores for significant savings.

How Does Baking Soda Work?

When you add sodium bicarbonate to pool water, it dissolves and releases bicarbonate ions directly into the water. These ions increase your total alkalinity reading predictably and reliably. I appreciate this chemical because it raises alkalinity substantially while having minimal impact on pH levels.

Through practical experience, I’ve found that 1.5 pounds of sodium bicarbonate per 10,000 gallons of water raises total alkalinity by approximately 10 ppm. This predictability lets me calculate doses accurately and avoid overcorrection, which creates more work fixing the opposite problem.

Alternative Chemicals That Can Increase Alkalinity

Sodium Carbonate (Soda Ash)

Sodium carbonate, commonly called soda ash or pH increaser, technically raises alkalinity too. However, I rarely use it for this purpose because it impacts pH much more dramatically than alkalinity. When I test a pool and find the pH at 7.8 but alkalinity at 60 ppm, adding soda ash would push the pH over 8.0 while barely addressing the alkalinity problem.

I keep soda ash in my service truck for specific situations where both pH and alkalinity need significant increases simultaneously. But even then, I often prefer raising alkalinity first with sodium bicarbonate, then addressing pH separately if needed. This sequential approach gives me better control over the final water chemistry.

When to Use What

After testing thousands of pools, I’ve developed a simple decision tree. If your alkalinity is low but pH is normal or high (above 7.4), use sodium bicarbonate exclusively. This describes about 90% of the situations I encounter. The baking soda raises alkalinity with minimal pH changes.

Consider sodium carbonate only when both alkalinity and pH are dangerously low (below 60 ppm alkalinity and below 7.0 pH). Even in these cases, many experienced pool technicians I know still prefer the sodium bicarbonate approach because it offers more precise control.

How to Properly Add Alkalinity Increaser

Testing Your Water First

I never add any chemical without testing first. It sounds basic, but I’ve seen too many pool owners dump chemicals based on assumptions rather than actual measurements. Invest in a quality test kit. I prefer liquid reagent kits over test strips because they’re more accurate, though good quality strips work fine for routine monitoring.

Test both alkalinity and pH because they interact. I’ve arrived at pools where someone added alkalinity increaser without checking pH first, then wondered why their water turned cloudy when the pH shot up past 8.2. These mistakes cost time and money to fix.

Step-by-Step Application Process

Calculating the Right Amount

Here’s the formula I use daily: For every 10 ppm increase needed in 10,000 gallons, add 1.5 pounds of sodium bicarbonate. So if your pool holds 20,000 gallons and alkalinity needs to rise from 60 to 100 ppm (a 40 ppm increase), you need 12 pounds total.

I always round down slightly on my initial dose. If calculations say 12 pounds, I might add 10 pounds first, wait 24 hours, retest, then add the remaining amount if needed. This conservative approach prevents overshooting, which takes days or weeks to correct.

Distribution and Circulation

The application technique matters more than most people realize. I walk around the pool perimeter, broadcasting the sodium bicarbonate evenly across the water surface. Dumping it all in one spot can create temporary high-concentration areas that might stain certain pool surfaces.

After adding the chemical, I run the circulation system for a minimum of 6 hours. The pump needs time to distribute the sodium bicarbonate throughout the entire water volume. I’ve tested pools where chemicals were added but circulation wasn’t run long enough, resulting in uneven chemistry readings across different areas of the pool.

I always tell clients to wait a full 24 hours before retesting. The sodium bicarbonate takes time to fully dissolve and integrate into the water chemistry. Testing too early gives false readings and leads to incorrect additional dosing.

Common Mistakes to Avoid When Adjusting Alkalinity

Adding Too Much Too Fast

The biggest mistake I see is impatience. Someone tests their pool, finds alkalinity at 50 ppm, calculates they need 8 pounds of sodium bicarbonate, then adds 12 pounds “to be safe.” Now alkalinity sits at 160 ppm, creating cloudy water, reduced chlorine efficiency, and scale formation.

When alkalinity gets too high, the only fix is adding acid, which lowers both pH and alkalinity. This becomes a slow, tedious process of adding small amounts of acid, waiting, testing, and repeating. I’ve spent weeks bringing down alkalinity that someone drove too high in a single afternoon.

If you need to make a large correction (more than 30 ppm), split it into multiple doses over several days. I might add half the calculated amount, wait 48 hours, retest, then add more if needed. This approach takes longer but prevents costly overcorrection.

Ignoring pH Levels

Alkalinity and pH move together, though not always proportionally. When I raise alkalinity with sodium bicarbonate, I expect pH to increase slightly, usually by 0.1 to 0.3 units. If pH starts at 7.8 and alkalinity needs correction, I might see pH climb to 8.0 or higher after treatment.

I monitor both measurements together and plan adjustments accordingly. Sometimes I need to lower pH slightly with muriatic acid after raising alkalinity. Other times, the pH settles into acceptable range naturally. The key is testing both parameters and understanding their relationship rather than treating them as independent variables.

Conclusion

After more than a decade maintaining pools professionally, I can confidently say that sodium bicarbonate remains the most effective, predictable, and affordable chemical for raising total alkalinity. Whether you buy it from a pool supply store or purchase baking soda in bulk, you’re getting the same reliable compound that stabilizes water chemistry and makes pool maintenance manageable.

The key to success lies not in the chemical itself but in proper testing, careful calculation, patient application, and understanding how alkalinity interacts with pH. Take your time, measure accurately, distribute the chemical evenly, and give it adequate circulation time. These practices, learned through years of hands-on experience, will keep your pool water balanced and comfortable.

Remember that maintaining proper alkalinity protects your investment in pool equipment, preserves your pool surfaces, and ensures swimmers enjoy comfortable, clear water. It’s worth the small effort to get it right.