Soda ash raises the pH of pool water. It’s the go-to chemical when your pool turns acidic (below 7.2), and it works fast because a 1% solution in water already has a pH of about 11.4. If you’ve tested your pool and found the pH is low, soda ash is likely what you need, but there are some important details about how it behaves, how much to use, and what can go wrong.
How Soda Ash Changes Pool Water
Soda ash is the common name for sodium carbonate. When you dissolve it in pool water, the sodium separates from the carbonate. That free carbonate then grabs a hydrogen ion from the surrounding water, and removing hydrogen ions is exactly what raises pH. The carbonate becomes bicarbonate in the process, which is the same compound that makes up your pool’s total alkalinity.
This is why soda ash doesn’t just raise pH. It also bumps up your total alkalinity, even if alkalinity wasn’t the thing you were trying to fix. If your alkalinity is already in the ideal range of 80 to 120 ppm and you only need to raise pH, soda ash is still the right choice. Just know that alkalinity will creep up too, and you may need to retest and adjust afterward.
When Your Pool Needs It
The ideal pH range for a residential pool is 7.2 to 7.8, with most pool operators aiming to stay between 7.4 and 7.6 to minimize swings in either direction. When pH drops below 7.2, the water becomes acidic enough to cause real problems. Acidic water corrodes pool infrastructure, including liners, pipes, pumps, and heater components, leading to expensive repairs over time. It also irritates skin and eyes and reduces the effectiveness of chlorine at the concentrations you’re used to.
Soda ash is the standard fix for low pH. If you also need to raise total alkalinity, soda ash gives you more effect per pound than sodium bicarbonate (baking soda), and it costs less too.
How Much to Add
The right dose depends on how far your pH has dropped and how many gallons your pool holds. Here’s a general dosage guide based on a widely used reference chart:
- pH 7.2 to 7.4: About 6 ounces per 10,000 gallons
- pH 7.0 to 7.2: About 8 ounces per 10,000 gallons
- pH 6.6 to 7.0: About 12 ounces per 10,000 gallons
- pH below 6.7: About 1 pound per 10,000 gallons
Never add more than 2 pounds per 10,000 gallons in a single treatment. If your pH is very low and needs a larger correction, add one dose, let the pump circulate the water fully, retest, and then add more if needed. Overshooting pH to the high side creates a different set of problems, so patience here saves you from chasing your numbers back and forth.
Soda Ash vs. Baking Soda
Both chemicals are alkaline, but they serve different purposes. Soda ash (sodium carbonate) raises pH much more aggressively because its solution pH is around 11.4. Baking soda (sodium bicarbonate) is milder, with a solution pH closer to 8.3, so it primarily raises total alkalinity without moving the pH needle as much.
The simple rule: if your pH is low but alkalinity is fine, use soda ash. If your alkalinity is low but pH is close to normal, use baking soda. If both are low, soda ash handles both at once and costs less pound for pound.
How to Add It Properly
Dumping dry soda ash powder directly into the pool is a common mistake. It can cloud the water immediately and may not dissolve evenly. The better approach is to pre-dissolve it in a bucket first.
Fill a bucket about three-quarters full with pool water. Slowly pour the measured amount of soda ash into the bucket and stir until the powder is completely dissolved. If you need more than one bucketful, work in batches, keeping each one under 15 pounds. Once fully dissolved, slowly pour about half the bucket into the pool near a return jet, then let fresh pool water into the bucket, stir again, and pour the rest. This dilution step prevents a concentrated slug of high-pH water from hitting the pool all at once.
Make sure the pump is running the entire time. Wear safety glasses and gloves when handling the powder, as concentrated sodium carbonate is irritating to skin and eyes.
Why Soda Ash Clouds the Water
If you’ve added soda ash and your pool turned milky white, you’re not alone. This is one of the most common side effects, and it happens because of calcium. When you add soda ash, you’re flooding the water with carbonate ions. Those carbonate ions find dissolved calcium in the pool and instantly form calcium carbonate, a white precipitate that makes the water look cloudy. The reaction happens fast and spreads quickly.
Pools with higher calcium hardness levels are more prone to this. The cloudiness is usually temporary and clears as the precipitate settles or gets filtered out, but it can take hours to a full day depending on your filter and circulation. Pre-dissolving the soda ash and adding it slowly helps reduce the severity. Pouring undissolved powder directly into the pool almost guarantees cloudiness because it creates localized pockets of extremely high pH where calcium carbonate forms aggressively.
If your pool has high calcium hardness (above 400 ppm), be especially cautious with soda ash doses. Smaller, spaced-out additions give the water time to equilibrate without overwhelming it with carbonate all at once.
After You Add Soda Ash
Let the pump run for at least one full turnover cycle before retesting. For most residential pools, that’s 6 to 8 hours. Retest both pH and total alkalinity, since soda ash affects both. If the pH still isn’t where you want it, repeat the process with another measured dose rather than guessing and adding extra.
Keep in mind that pH can drift after treatment as the water chemistry stabilizes. Testing again the following day gives you a more accurate picture of where things settled. If your alkalinity ended up higher than you’d like, you can bring it down later with small additions of muriatic acid while aerating the pool to keep pH from dropping too far.