Low pH is one of the most common pool water problems, and one of the most damaging if you ignore it. Acidic pool water corrodes metal equipment, etches plaster and concrete surfaces, irritates eyes and skin, and makes your chlorine burn off faster. Fixing it is straightforward and takes about 15 minutes of active work.
Here is how to raise your pool pH safely, what chemicals to use, and how to avoid overcorrecting.
What Is the Ideal Pool pH
The ideal pH range for a swimming pool is 7.2 to 7.6. The sweet spot is 7.4 to 7.6 for most pools.
At 7.2, chlorine is very effective but the water starts getting aggressive toward metal and surfaces. At 7.6, the water is comfortable but chlorine effectiveness begins to decrease. Above 7.8, chlorine becomes significantly less effective and the water tends to get cloudy.
You want to land in the middle. Test your pH at least twice a week during swimming season using a reliable pool test kit. Digital testers and liquid reagent kits are more accurate than test strips for pH measurement.
Why pH Drops
Understanding why your pH is low helps you fix the root cause instead of constantly chasing the number.
Chlorine Tablets (Trichlor)
This is the number one cause of chronically low pH in residential pools. Trichlor tablets have a pH of about 2.8, which is extremely acidic. Every tablet that dissolves slowly drags your pH down. If your only chlorine source is tablets, your pH will trend downward constantly.
Heavy Rain
Rainwater has a pH between 5.0 and 5.5 in most areas, and even lower in regions with acid rain. A heavy storm can dump enough acidic water into your pool to noticeably lower pH. It also dilutes alkalinity, which makes pH harder to stabilize.
Heavy Swimmer Load
Sweat, body oils, sunscreen, and urine (yes, really) are all acidic. A busy pool party with 15 people can drop pH measurably in a single afternoon.
Fresh Fill Water
Municipal water pH varies. Some municipal water supplies deliver water at 6.8 to 7.0. If you recently topped off or refilled a significant portion of your pool, the new water may have pulled pH down.
Organic Debris
Leaves, pollen, and other organic matter decompose in the pool and produce acidic byproducts. Pools near trees or in heavily wooded areas tend to have pH that drifts lower between cleanings.
Soda Ash vs. Baking Soda
These are the two chemicals used to raise pH in pools. They work differently and are not interchangeable.
Soda Ash (Sodium Carbonate)
Soda ash is the primary chemical for raising pH. It has a strong effect on pH with a moderate effect on total alkalinity. This is what you want when your pH is low but your alkalinity is within range or only slightly low.
Effect: 6 ounces of soda ash per 10,000 gallons raises pH by approximately 0.2.
Baking Soda (Sodium Bicarbonate)
Baking soda primarily raises total alkalinity with a mild effect on pH. Use this when both your alkalinity and pH are low. If your alkalinity is fine and only pH needs to come up, baking soda is the wrong tool because you will overshoot alkalinity before pH reaches the target.
Effect: 1.5 pounds of baking soda per 10,000 gallons raises alkalinity by approximately 10 ppm and pH by roughly 0.1 to 0.2.
Which One to Use
| Situation | Use This |
|---|---|
| Low pH, alkalinity in range (80-120 ppm) | Soda ash |
| Low pH AND low alkalinity | Baking soda first to raise alkalinity, then soda ash if pH still needs help |
| Low pH, high alkalinity (above 120 ppm) | Aeration (not chemicals) to raise pH without increasing alkalinity |
Step-by-Step: How to Raise Pool pH
Step 1: Test the Water
Test pH, total alkalinity, and free chlorine before adding anything. Write down the numbers. You need to know your starting point to calculate the correct dose.
Also test alkalinity because it directly affects how stable your pH adjustment will be. If alkalinity is low, raise that first with baking soda, then address pH.
Step 2: Calculate the Dose
For soda ash, start with 6 ounces per 10,000 gallons of pool water to raise pH by approximately 0.2. If your pool is 20,000 gallons and pH is 7.0 (you need to raise it 0.4), you would use about 24 ounces (1.5 pounds).
Always round down. It is much easier to add a little more later than to deal with pH that is too high. Overcorrecting is the most common mistake.
Step 3: Pre-Dissolve the Chemical
Dissolve soda ash in a bucket of warm pool water before adding it to the pool. Dumping dry powder directly into the pool can create concentrated spots that cloud the water and can even stain surfaces.
Stir until the powder is fully dissolved. It dissolves quickly in warm water.
Step 4: Add to the Pool
With the pump running, pour the dissolved solution around the pool perimeter, spreading it out as much as possible. Avoid pouring it all in one spot. Adding it near the return jets helps with distribution.
Do not pour chemicals into the skimmer. The concentrated solution can damage your pump, filter, and heater as it flows through the system.
Step 5: Wait and Circulate
Run the pump for at least 4 to 6 hours to fully circulate the treated water throughout the pool. pH adjustments need time to equalize.
Step 6: Retest
After 6 hours of circulation (or the next day), test pH again. If it is still low, repeat the process with another small dose. If it is within range, you are done.
If pH went too high (above 7.8), you will need to lower it with muriatic acid or sodium bisulfate. Our guide on how to lower pool chlorine covers related chemistry management.
Using Aeration to Raise pH
There is a third way to raise pH that does not involve adding any chemicals: aeration.
When you agitate the water surface and increase air exposure, carbon dioxide escapes from the water. Losing CO2 raises pH. This is the same process that makes a glass of soda water go flat and become less acidic over time.
You can aerate by:
- Running water features (fountains, waterfalls, spillovers)
- Pointing return jets upward to break the surface
- Running an air compressor with a hose in the pool
- Using a spa blower if your pool has a connected spa
Aeration raises pH without affecting total alkalinity, which makes it the ideal method when alkalinity is already high or at the top of the range and you only need to raise pH. The downside is that it is slow. It can take days of continuous aeration to raise pH significantly.
Common Mistakes
Adding Too Much at Once
The biggest mistake is dumping in a large dose to fix pH in one shot. pH is logarithmic, which means the difference between 7.0 and 7.2 is not the same chemical change as between 7.6 and 7.8. Always add less than you think you need, circulate, and retest.
Ignoring Alkalinity
If total alkalinity is low, your pH will not stay put no matter how much soda ash you add. It will bounce right back down. Fix alkalinity first (80 to 120 ppm), then address pH. Alkalinity is the buffer that holds pH stable.
Testing Too Soon
If you test 30 minutes after adding soda ash, you will get a misleading reading. The chemical has not fully distributed. Wait at least 4 to 6 hours before retesting.
Using the Wrong Chemical
Baking soda when you need soda ash (or vice versa) is a common mix-up. Remember: soda ash for pH, baking soda for alkalinity. Using baking soda to raise pH works but it also raises alkalinity, which you may not want.
Keeping pH Stable Long-Term
Raising pH once is easy. Keeping it stable is the real game. Here is what helps.
Maintain proper alkalinity. Keep total alkalinity between 80 and 120 ppm. This buffers pH against rapid swings.
Reduce trichlor tablet use. Switch to liquid chlorine or a saltwater system for daily sanitization and use tablets only as a supplement. This eliminates the main driver of chronic low pH.
Stay on a testing schedule. Test at least twice a week. Catching a small pH drift early is much easier than fixing a big one. Follow a consistent pool maintenance schedule and pH problems become rare.
Clean up debris promptly. Organic matter drives pH down as it decomposes. Skim, brush, and vacuum regularly.
If your pool chemistry has gone completely sideways and you are dealing with algae on top of pH issues, our green pool water fix guide covers how to handle multiple problems at once.
Frequently Asked Questions
How long does it take for soda ash to raise pool pH?
Soda ash begins working immediately on contact with the water, but it takes 4 to 6 hours of pump circulation for the pH change to fully equalize throughout the pool. Do not retest or add more chemical until you have circulated for at least that long. Testing too early can give you a falsely high or low reading depending on where you sample.
Can I use baking soda to raise pH?
Yes, but it is not ideal if your alkalinity is already in range. Baking soda primarily raises alkalinity and has a mild effect on pH. If your alkalinity is at 100 ppm and pH is 7.0, using baking soda will push alkalinity above the ideal range before pH reaches target. Use soda ash instead when only pH needs to come up.
How much soda ash to add to a pool?
As a starting guideline, use 6 ounces of soda ash per 10,000 gallons of pool water to raise pH by approximately 0.2 units. For a 15,000-gallon pool with a pH of 7.0 that you want to raise to 7.4, you would need about 18 ounces. Always add less than the calculated amount and retest after circulation. Pools vary and the actual result depends on alkalinity, temperature, and other factors.
Why does my pool pH keep dropping?
The most common cause is chlorine tablets (trichlor), which are highly acidic and steadily push pH down. Other causes include heavy rain, high swimmer load, and organic debris. If your pH drops constantly despite regular adjustment, switch to a less acidic chlorine source like liquid chlorine, cal-hypo shock, or a salt chlorine generator. Also check that your total alkalinity is adequate (80 to 120 ppm) since low alkalinity means pH has no buffer against swings.
Is low pH dangerous?
Water with pH below 7.0 can cause eye and skin irritation, corrode metal pool equipment (heaters, ladders, light housings), etch plaster and concrete surfaces, and degrade rubber gaskets and o-rings. It also makes chlorine hyperactive, meaning it burns off faster and provides inconsistent sanitization. While a pH of 7.0 to 7.2 is not immediately dangerous to swimmers, it is hard on your pool and equipment over time.