Pool pH too low? Here's how to raise it
A pH reading below 7.2 means your water is corrosive. It etches plaster, attacks grout and tile, eats metal fittings, and irritates swimmers' eyes — all while looking perfectly clear. Here's how to bring pH back up and keep it there.
Quick answer
Target pH: 7.4–7.6. Below 7.2, add soda ash (sodium carbonate) if alkalinity is in range, or baking soda if alkalinity is also low. Both raise pH — baking soda just raises alkalinity more in the process. Add near a return jet with the pump running, wait 4–6 hours, retest before adding more.
What low pH does to your pool
At normal pH (7.4–7.6), your water is in equilibrium — it neither attacks surfaces nor deposits minerals. Drop below 7.2 and it becomes undersaturated: it actively seeks calcium and minerals to reach equilibrium, and it finds them in your plaster, grout, and equipment.
| pH Range | Status | What It Does |
|---|---|---|
| Below 7.0 | Actively corrosive | Rapid surface etching, metal corrosion, equipment damage. Fix immediately |
| 7.0 – 7.2 | Too low | Ongoing surface attack, irritating to eyes and skin, equipment wear |
| 7.2 – 7.4 | Slightly low | Borderline — raise to 7.4+ before the next swim session |
| 7.4 – 7.6 | Ideal | No action needed. Chlorine most effective here |
| 7.7 – 7.8 | Slightly high | Add acid soon — chlorine starts losing effectiveness |
| 7.9+ | Too high | Significant chlorine loss, scale formation, cloudy water |
Soda ash vs baking soda: which to use
The right product depends on your total alkalinity (TA) reading:
| Situation | Use This | Why |
|---|---|---|
| pH low + TA in range (80–120 ppm) | Soda ash | Raises pH quickly with a smaller effect on TA |
| pH low + TA also low (<80 ppm) | Baking soda | Raises both TA and pH in one step; stabilizes pH long-term |
| pH low + TA already high (>120 ppm) | Borax | Raises pH without adding alkalinity; less common situation |
Why does this matter? Alkalinity is your pH buffer — it's what keeps pH stable between tests. If you raise pH with soda ash while TA remains low, pH will bounce right back down within a day or two. Fix TA first (or alongside), and pH holds on its own.
The order of operations
Always fix alkalinity first if TA is low. TA at 80–120 ppm stabilizes pH mechanically — you spend less time chasing pH if the buffer is right. Raise TA with baking soda, wait 4–6 hours, retest. If pH is still low after TA is in range, then add soda ash.
How to raise pH: step by step
- Test both pH and total alkalinity. You need both numbers to pick the right product and dose
- Calculate your dose. The exact amount depends on pool volume, current pH, and your target. Use the free pH calculator, or PoolChem Tracker calculates it automatically from your readings
- With the pump running, broadcast the product across the pool surface or add near a return jet. Don't dump it into the skimmer and don't pour the entire dose in one spot
- Wait 4–6 hours with circulation running
- Retest before adding more. Soda ash can overshoot pH if you add too much at once — underdosing is the safer approach
Why pool pH drops
Low pH is usually the result of one or more acidic inputs into your water:
- Trichlor tablets: The most common culprit. Trichlor has a pH of about 2.8 — every tablet you add pulls pH down. Heavy tablet use requires regular pH adjustments. Switching to liquid chlorine (pH ~13) dramatically reduces the pH decline
- Dry acid (sodium bisulfate): Used to lower pH and alkalinity. If overdosed or used frequently, it acidifies the water cumulatively
- Muriatic acid overdose: Easy to overshoot, especially on small pools. If you recently added acid to lower high pH and overcorrected, this is likely the cause
- Rain and acid rain: Rain typically has a pH of 5–6. A hard rain event can drop pool pH measurably, especially on smaller pools
- CO2 from algae or bather load: CO2 dissolves in water as carbonic acid. Heavy bather load and algae blooms can push pH down
Trichlor tablets and the pH cycle
Tablet pool owners often get into a pattern: add acid to lower high pH → wait a week → pH has dropped → add soda ash → repeat. Trichlor is the hidden driver. If this cycle sounds familiar, check your alkalinity — it's probably swinging too and making the whole system unstable. Consider whether liquid chlorine makes sense for your pool.
How much soda ash to add
Exact doses depend on your pool's volume and how much the pH needs to move, but a rough reference for a 15,000-gallon pool:
| Current pH | Target pH | Approx. Soda Ash (15k gal) |
|---|---|---|
| 7.0 | 7.4 | ~12–14 oz |
| 7.2 | 7.4 | ~6–8 oz |
| 7.2 | 7.6 | ~12–14 oz |
| 7.0 | 7.6 | ~18–22 oz |
These are starting-point estimates — always retest before adding a second dose. Soda ash can overshoot, and a pH that goes too high is its own problem.
Enter your pool volume, current pH, and target — get the exact amount of soda ash, baking soda, or muriatic acid to add.
Use the calculator →pH and alkalinity: fix both, not just one
Low pH often appears alongside low alkalinity — they have the same root causes (trichlor, acid rain, acid overdose). When both are low:
- Raise alkalinity first with baking soda. TA at 80–120 ppm gives pH somewhere to anchor
- Wait 4–6 hours and retest both
- If pH is still below 7.4 after TA is in range, add a small dose of soda ash
This approach is more reliable than fighting pH directly while TA remains unstable. A pool with good alkalinity is a pool where pH holds steady between test days.
See your pH and TA together
PoolChem Tracker tracks both readings side by side and recommends the right adjustment — soda ash, baking soda, or acid — based on exactly what your water needs.
Frequently asked questions
What happens if pool pH is too low?
Low pH (below 7.2) makes the water corrosive. It etches plaster and pebble surfaces, attacks grout, corrodes metal fittings and pump components, and irritates swimmers' eyes and skin. The damage is cumulative — your pool may look fine while surfaces are slowly being worn down. Below 7.0, damage accelerates significantly.
How do I raise pool pH?
Add soda ash (sodium carbonate) or baking soda (sodium bicarbonate) with the pump running, broadcast near a return jet. If TA is also low, use baking soda — it raises both. If TA is fine, use soda ash for a faster direct pH lift. Wait 4–6 hours and retest before adding more. Use a pH calculator to get the right dose for your pool volume.
Should I use soda ash or baking soda to raise pH?
Check your alkalinity first. If TA is below 80 ppm: baking soda, which raises both TA and pH. If TA is in range (80–120 ppm): soda ash, which raises pH with a smaller alkalinity effect. Using soda ash when TA is low tends to cause pH to rebound and drop again quickly, because there's no buffer to hold it in place.
Why does my pool pH keep dropping?
The most common cause is trichlor tablet use — trichlor has a pH of about 2.8 and pulls water pH down with each dose. Other causes: dry acid overdose, muriatic acid overcorrection, rain, and CO2 from algae or heavy bather load. If you're on tablets and fighting constant pH decline, check your alkalinity too — it's likely unstable as well, which makes pH harder to hold.
Pool Chemistry Basics Series
- Pool Chemistry for Beginners (start here)
- Pool chemistry cheat sheet
- Pool alkalinity vs pH
- How to balance pool water in 4 steps
- Baking soda vs soda ash
- Pool pH too high? How to fix it
- Pool pH too low? How to raise it
- Pool pH keeps rising
- Ideal pool pH level
- How to lower pool alkalinity
- How to raise pool alkalinity
- How much muriatic acid to add to a pool
- Does high alkalinity cause cloudy water?
Related reading
- Pool pH Too High? How to Fix It — the other direction: muriatic acid, dry acid, and when to address TA first
- Baking Soda vs Soda Ash — the full comparison of which product raises what and when to use each
- Pool Alkalinity vs pH — why these two readings are linked and which to fix first
- Pool pH calculator — exact dose of soda ash or acid for your pool volume