How to raise alkalinity in a pool
Add baking soda (sodium bicarbonate): 1.4 lb per 10,000 gallons raises total alkalinity (TA) by 10 ppm.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (10 sections)
For a 15,000-gallon pool going from 60 to 90 ppm, that is about 6.3 lb. Retest after the pump has run for about 6 hours.
Calculator: baking soda for your target
The rate above is the easy part. The calculator does the rest with your own numbers: your gallons, your TA now, and the TA you want. Enter them for a dose in pounds and ounces, split into smaller steps. For most pools the target is 80–120 ppm; the calculator's default of 90 ppm is well inside it. If your pool uses a salt water generator or liquid chlorine and pH keeps climbing, aim lower, around 70 ppm. Lower alkalinity slows the rise of pH. The alkalinity levels guide explains the trade-off, and the pool chemistry chart shows TA next to every other target.
The result is split into steps of up to 30 ppm. For a pool at 40 ppm aiming for 90, that means two steps with a retest in between, rather than one big pour based on a single test.
Raise TA without raising pH (and when that's impossible)
Strictly speaking, anything that adds alkalinity raises pH a little. What matters is how much. Compare the two common products for the example at the top (15,000 gallons, TA 60 → 90, starting pH 7.4, stabilizer (CYA) 30 ppm):
| Product | Amount | pH right after (model) |
|---|---|---|
| Baking soda (sodium bicarbonate) | 6.3 lb | about 7.54 |
| Soda ash (sodium carbonate) | 4.0 lb | above 9, off the scale of most test kits |
Closed-system carbonate model, before any CO2 exchange with the air. Soda ash is a pH product. Using it to raise TA by 30 ppm would push pH far too high.
So "raise alkalinity without raising pH" in practice means: use baking soda. If pH is already high (7.8 or more) and TA is low, do it in this order:
- Lower pH to about 7.2–7.4 with acid first (see how to lower pH). This removes a few ppm of TA.
- Add baking soda for the TA you need. pH will rise a little, landing near the middle of the range.
Where it is impossible: you cannot raise TA while lowering pH in one step. And if you add baking soda to water that already has high pH and high calcium, you risk scale and cloudiness. Fix pH first.
Step by step
- Test TA and pH (and free chlorine: pH and TA readings are unreliable when chlorine is above 10 ppm).
- If free chlorine is below your minimum, add chlorine first. Then handle alkalinity, then pH. The order to add pool chemicals guide explains why.
- Enter your numbers in the calculator and weigh out the first step (up to 30 ppm).
- With the pump running, spread the baking soda over a wide area of the deep end. In vinyl-liner pools, dissolve it in a bucket of pool water first.
- Brush any powder that settles on the floor.
- Let the pump run for several hours, then retest TA and pH. Add the next step only if you still need it.
- If pH is now low, correct it last with soda ash or aeration. See how to raise pH.
Always follow the product label.
How long it takes
Baking soda dissolves within minutes and starts working as soon as it mixes. The limit is circulation: the whole pool has to pass through the pump before a test from the side reads the same as one from the middle. A common practice is to wait about 6 hours before retesting. It is not a standard, and a small pump or a large pool may need a full day. A two-step correction (for example, 30 → 90 ppm) usually takes one day: one step in the morning and one in the evening.
Alkalinity first, then pH
When both TA and pH are low, raise TA first. Baking soda raises pH a little on its own, so after a TA correction pH often needs less help, or none. Correct pH last, after a retest. The only exception is chlorine: if free chlorine is below your minimum, add chlorine before anything else. The full sequence for every product is in the order to add pool chemicals, and the pool chemical calculator puts your own test in that order for you.
Soda ash vs baking soda
- Baking soda (sodium bicarbonate, pH about 8.3 in solution): mainly raises TA. Use it when TA is low.
- Soda ash (sodium carbonate, pH about 11 in solution): mainly raises pH, and TA along with it. Use it when pH is low and TA is fine.
Per pound, soda ash adds more alkalinity, which is why it can look like the cheaper TA product. The table above shows why it isn't: pH jumps, and then you pay for acid to bring it back down. Bags labeled "alkalinity increaser" are baking soda; bags labeled "pH increaser" are soda ash. More product detail, including a dose chart for every pool size, is on baking soda in a pool.
Low TA causes
- Acid. Every dose of muriatic or dry acid removes some alkalinity. Pools that need acid every week for rising pH slowly lose TA.
- Trichlor tablets. As tablet chlorine is used up, it consumes about 0.7 ppm of TA for each 1 ppm of chlorine. Pools on tablets tend to run low on TA.
- Rain and fresh water. Rain has almost no alkalinity, and some tap water is low too, so heavy rain or a big refill dilutes TA.
- On purpose. Salt pools and liquid-chlorine pools are often kept at 60–90 ppm to slow pH rise. That is "low" by the 80–120 rule, but not a problem if pH is stable.
High TA is the opposite problem and needs a different method: see how to lower alkalinity.
Details for pool technicians
- Formula. Baking soda needed (mg/L) = ΔTA × 84.007 / 50.043 = ΔTA × 1.679, with TA as ppm CaCO3. For 10,000 gallons (37,854 L) and +10 ppm that is 635 g, or 1.40 lb. Taylor's treatment table gives the same 1.40 lb.
- Steps. The calculator splits corrections into steps of up to 30 ppm, with a retest between them.
- What your test reads. A TA test also counts cyanurate from stabilizer, so at high CYA the carbonate part of TA is lower than the reading. That matters for the pH model and LSI, not for this dose: baking soda raises the reading by the amount shown.
FAQ
How do I raise alkalinity without raising pH?
Use baking soda, not soda ash. Raising TA by 30 ppm with baking soda raises pH by only about 0.1–0.15. If pH is already high, lower it with acid first, then add baking soda.
Does shocking a pool raise alkalinity?
Not in a way you can rely on. Liquid chlorine and cal-hypo (calcium hypochlorite) raise pH briefly when added, and most of that reverses as the chlorine is used up. Trichlor and dichlor lower TA over time. Use baking soda when TA is low.