How to raise pH in a pool
Raise pool pH with soda ash (sodium carbonate, sold as "pH increaser"), or with aeration if alkalinity is already high.
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 (12 sections)
In a 15,000-gallon pool with total alkalinity (TA) at 80 ppm and stabilizer (CYA) at 30 ppm, about 2.05 lb of soda ash takes pH from 7.1 to 7.5: add 1.65 lb first, then retest.
Calculator: soda ash or borax dose
The amount depends on numbers only your test shows: pH, alkalinity, and stabilizer. Enter pH now, target pH (7.4–7.6 is a good target), total alkalinity (TA), stabilizer (CYA), borates if any, and your volume. Choose soda ash (sodium carbonate, sold as "pH up" or "pH increaser") or borax (sodium tetraborate decahydrate, the laundry booster). The calculator splits the job into steps of up to 0.3 pH and rounds down, because it is easier to add more than to undo an overshoot.
The dose depends on your alkalinity: the more buffer in the water, the more product it takes to move pH. Here is the same 7.2 → 7.5 correction in 10,000 gallons:
| Total alkalinity | Soda ash | TA rise | Borax | TA rise | Borates added |
|---|---|---|---|---|---|
| 60 ppm | 11.7 oz | +8.3 ppm | 1.45 lb | +4.6 ppm | +2.0 ppm B |
| 80 ppm | 14.8 oz | +10.5 ppm | 1.8 lb | +5.8 ppm | +2.5 ppm B |
| 100 ppm | 1.1 lb | +12.7 ppm | 2.2 lb | +7.0 ppm | +3.0 ppm B |
| 120 ppm | 1.3 lb | +14.9 ppm | 2.6 lb | +8.2 ppm | +3.5 ppm B |
Rounded down. Borax adds about half as much alkalinity as soda ash for the same pH change, but you need roughly twice the weight and it leaves borate behind.
Check against a reference: for pH 7.2 → 7.5 at TA 80 in 10,000 gallons, the legacy TFP (Trouble Free Pool) calculator gives 14.7 oz of soda ash and our model gives 14.8 oz (details on the methodology page). For borax as a long-term buffer, see borax in a pool.
pH vs alkalinity: which to raise
Look at both numbers before you buy anything:
| Your test | What to do |
|---|---|
| pH low, TA low (below 80 ppm) | Raise TA first with baking soda, retest, then top up pH with soda ash or aeration |
| pH low, TA in range | Soda ash, or aeration for a small rise without adding TA |
| pH low, TA high | Aeration only: raises pH while TA stays where it is |
| pH fine, TA low | Baking soda: it raises TA with only a small pH change |
Taylor's guidance is clear: "Always bring total alkalinity into range before adjusting pH." Baking soda amounts and how little it moves pH are on baking soda in a pool. The full alkalinity plan is on how to raise alkalinity.
What happens when pH is too low
Below pH 7.2, water becomes corrosive and starts to dissolve the surfaces and metals it touches. Plaster and grout etch, metal parts (heater, ladder, pump seals) corrode and can stain the pool later, and vinyl liners can wrinkle. Swimmers notice it first as stinging eyes and itchy skin. Chlorine is also used up faster. A pH of 7.0–7.1 for a day is not an emergency, but correct it the same day rather than waiting for the weekly test.
pH increaser vs baking soda
They are different chemicals. "pH increaser" or "pH up" is soda ash (sodium carbonate): it moves pH a lot and TA a little. "Alkalinity increaser" is baking soda (sodium bicarbonate): it moves TA a lot and pH only a little. Use soda ash when pH is low and TA is fine; use baking soda when TA is low. Read the active ingredient on the bag, not the brand name. Baking soda doses are on how to raise alkalinity.
Does shocking a pool raise pH?
A little, and only for a while. Liquid chlorine and calcium hypochlorite (cal-hypo) raise pH right after you add them, and most of that rise goes away as the chlorine is used up. Trichlor and dichlor do the opposite and slowly lower pH. Don't use shock to fix pH; use soda ash or aeration. Test pH once chlorine is back in its normal range, because a very high chlorine level can make the pH test read wrong.
Aeration: raise pH naturally, without chemicals
Aeration drives carbon dioxide (CO2) out of the water. Losing CO2 raises pH but does not change total alkalinity, which makes it the only way to raise pH while keeping TA where it is. How to do it:
- Run waterfalls, fountains, spillovers, and bubblers.
- Point return jets up so they break the surface.
- Run the pump longer and remove the cover.
It is much slower than soda ash, and the speed depends on how hard the water is splashed, how warm it is, and how high TA is. We could not find a published rate, so retest daily instead of guessing. Stop when pH reaches about 7.5, or it will keep rising.
Why pH drops (trichlor, rain, acid overdose)
- Trichlor tablets. They are acidic and, as their chlorine is used up, they also use up alkalinity: about 0.7 ppm of TA for every 1 ppm of chlorine delivered (from the chemistry of trichlor). Tablet pools drift down in both pH and TA over the season.
- Rain. Rainwater is usually slightly acidic and has almost no alkalinity, so heavy rain lowers pH and dilutes TA.
- Too much acid. A big "rule of thumb" dose of muriatic acid is the fastest way to drop pH too far. Dose in steps with the acid calculator next time.
- Low alkalinity. With little buffer, small inputs move pH a lot. Fix TA, and pH becomes steadier.
Max per dose and retest
We limit each soda ash or borax step to +0.3 pH. That's our safety margin, not a standard: a wrong reading or a wrong volume then costs you a small correction, not cloudy water. After each step:
- Dissolve the dose in a bucket of warm pool water (product into water).
- Pour it slowly around the deep end in front of a return jet, with the pump running.
- Wait about 30 minutes, then retest pH.
- Add the next step only if you are still below your target.
Always follow the product label. Keep soda ash away from acid containers, and never mix it with other pool chemicals in the bucket.
Cloudy after soda ash?
A white haze right after adding soda ash usually means calcium carbonate: where the product lands, pH spikes locally and calcium in the water comes out as fine particles. It is most likely in hard water or when a lot is added at once. Keep the pump running and the filter clean; it usually clears within a day. Next time, dissolve it first, pour it slowly across a wide area, and stay within 0.3 pH per step. If haze persists or scale appears, check your water balance with the pH levels guide and your calcium reading, or see cloudy pool water. Every target in one table: the pool chemical chart.
Details for pool technicians
- Model. The dose comes from a carbonate model with corrections for cyanurate (CYA) and borate buffering, at 1,000 ppm TDS. Soda ash adds 2 equivalents of alkalinity per mole, so every dose also raises TA; the calculator shows by how much.
- Check. pH 7.2 → 7.5, TA 80, CYA 30, 10,000 gallons: our model 14.8 oz of soda ash, the legacy TFP calculator 14.7 oz.
- Rounding. Doses are rounded down and capped at +0.3 pH per step. The full formula is on the methodology page.
FAQ
How to raise pH in pool without raising alkalinity?
Aerate. Fountains, waterfalls, and jets aimed at the surface drive out carbon dioxide, which raises pH while total alkalinity stays the same. Borax is the next best option: it raises TA about half as much as soda ash for the same pH change.
What causes pool pH to drop?
Trichlor tablets, rain, too much acid, and low alkalinity. Trichlor is acidic and consumes alkalinity as it works, so pools chlorinated with tablets usually need pH and TA raised during the season.
Sources
- Taylor Technologies, K-1005 instruction manual (TA before pH): PDF
- PHTA technical bulletin, Boric acid and sodium borates: phta.org
- Secondary, used only to cross-check the pH model: legacy TFP pool calculator, legacy.poolcalculator.com