Sodium bicarbonate, commonly known as baking soda, is used in swimming pools primarily to raise total alkalinity. It’s one of the most frequently added chemicals in pool maintenance, and it works by increasing the water’s ability to resist sudden pH swings. If your pool’s alkalinity has dropped below the recommended range, sodium bicarbonate is the standard fix.
How It Works in Pool Water
Pool water stays balanced through a natural buffering system involving three related chemical forms: carbonic acid, bicarbonate, and carbonate. These three exist in a constant balancing act, and together they determine how stable your water chemistry is. When you add sodium bicarbonate, you’re adding bicarbonate ions directly into that system, which increases the water’s buffer capacity. A stronger buffer means your pH doesn’t spike or crash every time someone cannonballs in or the sun heats the surface.
The practical effect: sodium bicarbonate raises total alkalinity significantly while nudging pH up only slightly. One pound of sodium bicarbonate added to 10,000 gallons of water raises total alkalinity by about 7 ppm. That same dose raises pH by an amount so small it won’t even register on a standard pool test kit. This makes it the right tool when your alkalinity is low but your pH is already in a reasonable range.
Sodium Bicarbonate vs. Soda Ash
Pool owners often confuse sodium bicarbonate (baking soda) with sodium carbonate (soda ash), but they do different jobs. The industry standard is to use sodium bicarbonate when you need to raise total alkalinity and soda ash when you need to raise pH. The exception is when both readings are low, in which case soda ash can address both at once.
If you use soda ash when you only need to fix alkalinity, you’ll overshoot your pH. If you use sodium bicarbonate when your pH is the real problem, you’ll barely move the needle on pH while pushing alkalinity higher than necessary. Choosing the right one starts with testing both values.
What Happens When Alkalinity Is Too Low
Low total alkalinity means your water has lost its buffering ability. Without that buffer, pH becomes unstable and can swing dramatically from something as routine as rain, heavy swimmer use, or adding chlorine. The water also turns corrosive. Acidic, low-alkalinity water attacks metal components like ladders, handrails, light fixtures, and pump internals, shortening their lifespan and raising your long-term maintenance costs. It can also etch plaster and concrete pool surfaces, creating rough spots that are uncomfortable underfoot and harder to keep clean.
What Happens When Alkalinity Is Too High
Overcorrecting with sodium bicarbonate creates its own set of problems. High alkalinity pushes pH upward and makes it stubbornly difficult to bring back down. It also raises calcium saturation levels, which leads to scale buildup on tile, inside pipes, and on filter elements. You’ll notice the water turning cloudy, filters clogging faster, and potentially skin and eye irritation for swimmers. If you’ve added too much, you’ll need to lower alkalinity with muriatic acid or a dry acid product.
Target Ranges for Total Alkalinity
The Model Aquatic Health Code, which sets standards for public pools in the U.S., specifies a total alkalinity range of 60 to 180 ppm. For residential pools, many manufacturers and pool professionals recommend a tighter window of 110 to 150 ppm as the sweet spot for keeping pH stable and water comfortable. Your ideal number within that range depends on your sanitizer type, pool surface material, and local water chemistry, so it’s worth checking your pool builder’s or equipment manufacturer’s recommendations.
How Much to Add
A common guideline is 1.5 pounds of sodium bicarbonate per 10,000 gallons of water to raise total alkalinity by about 10 ppm. State health department guidelines for public pools suggest a similar figure of roughly 1.4 pounds per 10,000 gallons for a 10 ppm increase. The numbers vary slightly depending on the source because real-world pool conditions differ, but either figure gets you close.
To calculate your dose, you need two things: your pool’s volume in gallons and your current alkalinity reading from a test kit or test strip. Subtract your current reading from your target, figure out how many 10 ppm increments you need, and multiply by 1.5 pounds per 10,000 gallons. For a 20,000-gallon pool that needs a 20 ppm boost, that’s about 6 pounds of sodium bicarbonate. It’s better to undershoot slightly and retest after a few hours than to dump in too much and create a high-alkalinity problem.
How to Add It to Your Pool
Sodium bicarbonate dissolves readily, but adding a large quantity in one spot can create a localized zone of high alkalinity near the surface. The best practice is to broadcast it across the pool’s surface with the pump running, spreading it as evenly as possible. If you’re adding more than about 5 or 6 pounds, consider splitting the dose across two applications a few hours apart, testing between rounds. Wait at least 6 hours, ideally a full turnover cycle of your filtration system, before retesting to see where your alkalinity landed.
Many commercial “alkalinity increaser” products sold at pool supply stores are simply sodium bicarbonate with a pool-specific label and a markup. Buying plain baking soda, or pool-grade sodium bicarbonate in bulk bags, does the same job at a fraction of the cost.
Storage and Handling
Sodium bicarbonate is one of the safer pool chemicals, but it still needs proper storage. The EPA recommends keeping all pool chemicals in a designated storage area where water cannot contact the containers, ideally on shelves or pallets off the floor. Even though sodium bicarbonate itself isn’t hazardous in the way chlorine products are, it should be stored separately from acids and oxidizers. Mixing incompatible pool chemicals, even accidentally through spills or shared scoops, can cause dangerous reactions. Keep containers sealed, dry, and away from combustible materials, and never store different pool chemicals stacked above one another where a leak could cause cross-contamination.