pH and Alkalinity Adjustment Chart
A pH and alkalinity dosing chart: how much muriatic acid to lower pH, soda ash to raise pH, and baking soda to raise total alkalinity for pools from 5,000 to 40,000 gallons.
Quick answer (per 10,000 gallons): lower pH about 0.2 with 12 fl oz of 31% muriatic acid; raise pH about 0.2 with 6 oz of soda ash; raise total alkalinity 10 ppm with 1.5 lb of baking soda; lower TA 10 ppm with 25 fl oz of muriatic acid plus aeration to bring pH back up. Adjust alkalinity first, then pH. Add about three quarters of any dose, circulate, and retest before adding more.
Safety first, every time. Muriatic acid is corrosive: wear gloves and eye protection, work outdoors away from your face, and always add acid to water, never water to acid. Never mix acid with chlorine or any other pool chemical, since the combination can release toxic gas. Add one chemical at a time with the pump running, retest before re-dosing, and store acid, soda ash, and baking soda sealed, separated, and away from children and pets. These figures are estimates from standard pool-care formulas, so test your own water and follow your product labels.
pH and total alkalinity move together, so this chart covers both. Aim for pH between 7.2 and 7.8 (7.5 is the comfortable target) and TA between 60 and 120 ppm (around 90 is ideal); the full target ranges are in the pool chemistry levels chart. Confirm your gallons with the pool volume calculator, fix alkalinity first, then fine-tune pH. For a dose computed from your exact readings, use the pH & alkalinity calculator.
Muriatic acid chart: lower pH
Fluid ounces of 31 percent muriatic acid to lower pH by the amount shown, assuming total alkalinity near 100 ppm. One cup is 8 fl oz. Higher TA buffers the water and needs more acid; lower TA needs less. Acid also pulls TA down with every dose.
| Pool volume | Lower pH 0.1 | Lower pH 0.2 | Lower pH 0.3 | Lower pH 0.4 |
|---|---|---|---|---|
| 5,000 gal | 3 fl oz | 6 fl oz | 9 fl oz | 12 fl oz (1.5 cups) |
| 10,000 gal | 6 fl oz | 12 fl oz (1.5 cups) | 18 fl oz | 24 fl oz (3 cups) |
| 15,000 gal | 9 fl oz | 18 fl oz | 27 fl oz | 36 fl oz (4.5 cups) |
| 20,000 gal | 12 fl oz (1.5 cups) | 24 fl oz (3 cups) | 36 fl oz | 48 fl oz (1.5 quarts) |
| 25,000 gal | 15 fl oz | 30 fl oz | 45 fl oz | 60 fl oz |
| 30,000 gal | 18 fl oz | 36 fl oz (4.5 cups) | 54 fl oz | 72 fl oz (2.25 quarts) |
| 40,000 gal | 24 fl oz (3 cups) | 48 fl oz (1.5 quarts) | 72 fl oz | 96 fl oz (3 quarts) |
Pour acid slowly into the deep end near a return jet with the pump running, or pre-dilute in a bucket of pool water per the label. Using dry acid (sodium bisulfate) instead? Substitute about 10 oz by weight for every 12 fl oz of muriatic acid, and note that it adds sulfates over time.
Soda ash chart: raise pH
Ounces by weight of soda ash (sodium carbonate) to raise pH by the amount shown. Soda ash also lifts TA slightly. Add it slowly with the pump running, since a dumped-in dose can cloud the water briefly.
| Pool volume | Raise pH 0.1 | Raise pH 0.2 | Raise pH 0.3 | Raise pH 0.4 |
|---|---|---|---|---|
| 5,000 gal | 1.5 oz | 3 oz | 4.5 oz | 6 oz |
| 10,000 gal | 3 oz | 6 oz | 9 oz | 12 oz |
| 15,000 gal | 4.5 oz | 9 oz | 13.5 oz | 18 oz (1.1 lb) |
| 20,000 gal | 6 oz | 12 oz | 18 oz (1.1 lb) | 24 oz (1.5 lb) |
| 25,000 gal | 7.5 oz | 15 oz | 22.5 oz (1.4 lb) | 30 oz (1.9 lb) |
| 30,000 gal | 9 oz | 18 oz (1.1 lb) | 27 oz (1.7 lb) | 36 oz (2.3 lb) |
| 40,000 gal | 12 oz | 24 oz (1.5 lb) | 36 oz (2.3 lb) | 48 oz (3 lb) |
If pH runs chronically low along with low alkalinity, fix TA with baking soda first; it often brings pH most of the way up on its own.
Baking soda chart: raise total alkalinity
Pounds of baking soda (sodium bicarbonate, sold as alkalinity increaser) to raise TA by the amount shown. It barely moves pH, which is exactly why it is the right tool for alkalinity. Broadcast over the deep end with the pump running.
| Pool volume | Raise TA 10 ppm | Raise TA 20 ppm | Raise TA 30 ppm | Raise TA 40 ppm |
|---|---|---|---|---|
| 5,000 gal | 0.8 lb | 1.5 lb | 2.3 lb | 3 lb |
| 10,000 gal | 1.5 lb | 3 lb | 4.5 lb | 6 lb |
| 15,000 gal | 2.3 lb | 4.5 lb | 6.8 lb | 9 lb |
| 20,000 gal | 3 lb | 6 lb | 9 lb | 12 lb |
| 25,000 gal | 3.8 lb | 7.5 lb | 11.3 lb | 15 lb |
| 30,000 gal | 4.5 lb | 9 lb | 13.5 lb | 18 lb |
| 40,000 gal | 6 lb | 12 lb | 18 lb | 24 lb |
Muriatic acid chart: lower total alkalinity
Fluid ounces of 31 percent muriatic acid to lower TA by the amount shown. Acid drops pH at the same time, so the standard high-TA routine is: dose acid, then aerate (point returns upward, run a fountain or waterfall) to raise pH back without raising TA, and repeat until both land in range.
| Pool volume | Lower TA 10 ppm | Lower TA 20 ppm | Lower TA 30 ppm |
|---|---|---|---|
| 5,000 gal | 13 fl oz | 25 fl oz | 38 fl oz |
| 10,000 gal | 25 fl oz (3 cups) | 50 fl oz | 75 fl oz |
| 15,000 gal | 38 fl oz | 75 fl oz | 113 fl oz |
| 20,000 gal | 50 fl oz (1.5 quarts) | 100 fl oz (3 quarts) | 150 fl oz |
| 25,000 gal | 63 fl oz | 125 fl oz (1 gal) | 188 fl oz (1.5 gal) |
| 30,000 gal | 75 fl oz | 150 fl oz | 225 fl oz (1.75 gal) |
| 40,000 gal | 100 fl oz (3 quarts) | 200 fl oz (1.6 gal) | 300 fl oz (2.3 gal) |
Never try to drop very high TA in one giant dose; work down in 10 to 20 ppm steps with retests in between so pH never crashes. The chemistry behind the acid-then-aerate method is covered in total alkalinity explained.
pH and alkalinity adjusters
CPDI Muriatic Acid for Pools, 4-Pack
$56.79 on Amazon
Standard 31 percent pool acid for lowering pH and alkalinity.
Clorox Pool&Spa Swimming Pool Alkalinity Increaser, 5 lb
$10.94 on Amazon
Sodium bicarbonate to raise total alkalinity into range.
How to use these charts
- Alkalinity first, pH second. TA is the buffer; set it in range and pH becomes easy to steer.
- Add three quarters, then retest. pH doses in particular depend on your alkalinity, so treat every figure as a starting point, not a prescription.
- Give it time to mix. Run the pump a few hours before retesting; testing too soon reads low and tempts an overdose.
- Expect interaction. Acid lowers both pH and TA; soda ash raises both. Retest the other number after any adjustment.
- Watch the balance picture. pH, TA, calcium, and temperature together set whether water corrodes or scales; check the result against the saturation index chart.
For why these two numbers behave the way they do, read pool water balance, and keep the chemical dosing cheat sheet nearby for every other dose. These figures are estimates from standard pool-care formulas: your real result depends on your exact volume, current chemistry, and product strength, so always dose to your own test results.
Frequently Asked Questions
How much muriatic acid lowers pH from 7.8 to 7.4?
In 10,000 gallons with alkalinity near 100 ppm, dropping pH by 0.4 takes roughly 24 fluid ounces (3 cups) of 31 percent muriatic acid. A 20,000 gallon pool needs about 48 fluid ounces. The exact amount depends heavily on your total alkalinity, since higher TA buffers against the change, so add about three quarters of the chart dose, circulate for a few hours, and retest before adding more.
How much baking soda raises alkalinity by 10 ppm?
About 1.5 pounds of baking soda (sodium bicarbonate) raises total alkalinity by 10 ppm in 10,000 gallons. That scales linearly: 3 pounds for 20,000 gallons, or 0.75 pounds for 5,000 gallons. Alkalinity increaser sold at pool stores is the same chemical. Broadcast it over the deep end with the pump running and give it several hours of circulation before retesting.
Should I adjust alkalinity or pH first?
Alkalinity first, always. TA is the buffer that holds pH steady, so adjusting pH while alkalinity is out of range means chasing a moving target. Bring TA into the 60 to 120 ppm band, retest pH after the water mixes, and only then fine-tune pH. Correcting alkalinity often moves pH partway to where you want it on its own, which saves chemicals and frustration.
Does muriatic acid lower alkalinity too?
Yes. Acid lowers pH and total alkalinity at the same time; about 25 fluid ounces of 31 percent muriatic acid lowers TA by 10 ppm in 10,000 gallons. That is why the standard method for high TA is to dose acid to bring TA down, then aerate the water (fountains, returns pointed up, waterfalls) to raise pH back up without raising TA. Always retest both numbers after any acid addition.
Can I raise pH with baking soda?
Not really. Baking soda mostly raises total alkalinity and only nudges pH slightly, so it is the right tool when TA is low but pH is close. To raise pH itself, use soda ash (sodium carbonate): about 6 ounces raises pH roughly 0.2 in 10,000 gallons and lifts TA a little as well. If both pH and TA are low, correct TA with baking soda first and recheck pH before reaching for soda ash.
What about dry acid instead of muriatic acid?
Dry acid (sodium bisulfate) is a granular alternative that is easier to store and handle; about 10 ounces lowers pH roughly 0.2 in 10,000 gallons. The trade-off is that it adds sulfates with every dose, which can eventually harm plaster and salt cell plates, so many salt pool owners avoid it. Whichever acid you use, pre-dilute or pour per the label, add acid to water, and never mix it with chlorine.
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