How to Raise pH in a Pool: Soda Ash, Bicarb or Aeration

Name: comparepoolquotes
Price range: $$$

To raise pH in a pool, add soda ash (sodium carbonate) in small doses with the pump running, or aerate if alkalinity is already high. For a 50,000 litre pool at pH 6.8–7.0, two soda ash labels give 400 g, matching NSW Health’s chart from 7.0 to 7.5. Re-test after 3–5 hours; the target is 7.2–7.6.

The short answer

Soda ash dose: 400 g for a 50,000 litre pool at pH 6.8–7.0, on two Australian labels (80 g per 10,000 litres); NSW Health’s chart gives the same 0.4 kg to take 50 kL from 7.0 to 7.5.
Every alkali adds alkalinity: by our arithmetic 400 g of soda ash adds about 7.6 ppm in 50,000 litres, and the 800 g of bicarb NSW Health gives for the same job adds about 9.5 ppm.
Aeration raises pH and adds no alkalinity, because alkalinity is independent of carbon dioxide exchange (USGS); it is slow, hours to a couple of days.
Choose by your alkalinity reading: under 60 ppm use bicarb; 60–120 ppm use soda ash in small doses; above 120 ppm aerate first.
Target pH 7.2–7.6 for a home pool (SA Health); HealthyWA allows 7.2–7.8 with 7.5 ideal. NSW Health says below 7.2 causes bather discomfort and equipment corrosion.

Raising pH in a 50,000 litre pool: soda ash and bicarb doses from two labels and NSW Health, and the alkalinity each adds (labels and chart read 4 October 2026; alkalinity is our arithmetic)
pH now	Soda ash, label A (×5)	Soda ash, label B (×5)	NSW Health chart to pH 7.5, 50 kL	Alkalinity added by that soda ash dose	Aeration
7.0–7.2	200 g (40 g per 10,000 L)	300 g (60 g per 10,000 L)	0.4 kg soda ash or 0.8 kg bicarb, from 7.0	about 4–6 ppm (200–300 g)	Often enough on its own; adds 0 ppm
6.8–7.0	400 g (80 g per 10,000 L)	400 g (80 g per 10,000 L)	0.4 kg soda ash or 0.8 kg bicarb, from 7.0	about 7.6 ppm	Adds 0 ppm, but slow from this low
Below 6.8	500 g (100 g per 10,000 L)	500 g (100 g per 10,000 L)	0.6 kg soda ash or 1.2 kg bicarb, from 6.5	about 9.4 ppm (500 g)	Too slow alone; dose, then check why
About 6.0	No separate band: dose 500 g, re-test, repeat	As label A	0.9 kg soda ash or 1.8 kg bicarb	about 17 ppm (900 g)	Find the cause first (see below)

How do I raise the pH in my pool? Three ways, and which is which

Queensland Health’s pool guidelines put it in one line: if pH is too low, sodium carbonate (soda ash) ‘can be used to raise it quickly’, sodium bicarbonate (bicarb soda) raises it more slowly, and ‘increasing the pH in this way also increases total alkalinity’. NSW Health adds that bicarb overdosing will not raise pH above 8.3, while soda ash is a strong alkali that should be added slowly.

Soda ash (pH increaser, pH up): the fast option. Dissolve in a bucket of pool water and add in front of a return with the pump running. One label says not to add more than 10 g per 1,000 litres at a time (500 g for 50,000 litres) and to wait 4–5 hours before re-testing; another says 3 hours.
Bicarb (buffer): the gentle option, and the right one when alkalinity is also low. Its doses are on how to raise alkalinity without raising pH.
Aeration: point the returns up at the surface and run water features. It drives carbon dioxide out of the water, which raises pH; the USGS field manual says alkalinity is independent of carbon dioxide exchange, so it adds no alkalinity at all.

The quotable version: soda ash and bicarb both raise pH and alkalinity together; only aeration raises pH alone.

How much soda ash to raise pH in a 50,000 litre pool

Two Australian soda ash labels give doses per 10,000 litres: 100 g below pH 6.8 and 80 g at 6.8–7.0 on both; at 7.0–7.2 one says 40 g and the other 60 g. Multiply by five for 50,000 litres: 500 g, 400 g, and 200–300 g.

Cross-check against NSW Health. Its public-pool dosage chart (Table 5.3) gives bicarb to raise pH to 7.5, with a note that soda ash takes half the weight: 2 kg of bicarb equals 1 kg of soda ash. For 50 kL starting at pH 7.0 that is 0.8 kg of bicarb or 0.4 kg of soda ash, the same as the labels’ 6.8–7.0 band. From 6.5 it is 0.6 kg of soda ash; from 6.0, 0.9 kg.

What it does to alkalinity (our arithmetic). Soda ash supplies one milliequivalent of alkalinity per 53 mg, and the USGS conversion is 50.04 mg/L of alkalinity per milliequivalent. So each 100 g in 50,000 litres adds about 1.9 ppm: 400 g adds about 7.6 ppm. NSW Health’s equivalent 800 g of bicarb adds about 9.5 ppm. The difference between the two is smaller than their reputations suggest; bicarb’s real advantage is that it cannot overshoot past 8.3.

Neither the labels nor the chart say what alkalinity they assume, and higher alkalinity resists a pH change more. Dose, wait, re-test. Not sure of your volume? What it costs to fill a pool shows how to work it out from length, width and average depth.

For a 50,000 litre pool at pH 6.8–7.0, about 400 g of soda ash is the label dose, and it adds roughly 7.6 ppm of total alkalinity.

How to raise pH in a pool without raising alkalinity

Aerate. It is the only method that adds no alkalinity, and it is the right one when pH is low but alkalinity is normal or high, typically just after an acid dose. The method:

Turn the return eyeballs to point up so they break the surface.
Run any fountain, waterfall, spa spillover or bubbler.
Run the pump, and re-test pH every few hours.

How long it takes depends on how hard you aerate and how far pH has to go. A 2016 US trade-magazine article estimates pH can climb from 6.5 to 7.0 within a day with modest aeration, but take more than a day or two to get from 7.0 to 7.5 without significant aeration. Those are one author’s estimates, not Australian measurements.

Aeration is also the second half of lowering alkalinity: acid takes alkalinity and pH down together, then air brings pH back. When high alkalinity is clouding the water, see why a pool goes cloudy.

Raising pH ‘naturally’ means aeration: it is free and adds no alkalinity, and the trade-off is that it takes hours to days rather than minutes.

Which to use: the alkalinity-first rule

Test total alkalinity before choosing, then:

Alkalinity under 60 ppm (below SA Health’s home range of 60–200 mg/L): use bicarb. It raises the alkalinity you are short of and nudges pH up with it.
Alkalinity 60–120 ppm: use soda ash in small doses, or aerate if the pH is only just under 7.2.
Alkalinity above 120 ppm: aerate first. Adding alkali to high-alkalinity water moves you further from NSW Health’s 80–100 ppm ideal for pH-raising sanitisers such as liquid chlorine.

The 60 ppm line is SA Health’s; the 120 ppm line is our working threshold, sitting at the top of NSW Health’s ideal for pH-lowering disinfectants. Treat it as a guide, not a regulation.

When pool pH is low, the alkalinity reading decides the product: bicarb if alkalinity is low, soda ash if it is normal, aeration if it is high.

Why does my pool pH keep dropping?

Acidic sanitisers. NSW Health’s table of chlorine compounds lists trichlor (stabilised chlorine tablets) as lowering pH. Queensland Health’s troubleshooting table lists ‘acidic disinfectant used’ with the fix of regular alkali dosing.
Acidic top-up water. Queensland Health lists acidic mains water as a cause; HealthyWA lists heavy rain among the things that move pH.
Too much acid last time. On a pool where pH normally drifts up and is corrected with acid, an over-generous dose is the first suspect. The acid doses are on how to lower pH in a pool.
Low alkalinity. Queensland Health says water with alkalinity too low is not buffered, and pH changes rapidly.

If the cause is equipment, such as a chlorinator or an automatic dosing unit that needs replacing, pool equipment explained sets out the parts, and you can compare pool quotes from businesses in Sydney, Brisbane, Melbourne or Perth.

A pool whose pH keeps falling usually has an acidic sanitiser, acidic top-up water or low alkalinity behind it, and the alkalinity test is the first one to do.

Common questions

How do I raise the pH in my pool quickly?

Soda ash. Two labels give 80 g per 10,000 litres at pH 6.8–7.0, which is 400 g for 50,000 litres. Queensland Health says soda ash raises pH quickly and bicarb more slowly. Re-test after 3–5 hours.

How do I raise pH without raising alkalinity?

Aerate: point the returns up and run water features. The USGS field manual says alkalinity is independent of carbon dioxide exchange, so driving off carbon dioxide raises pH without adding alkalinity.

Can I raise pool pH with baking soda?

Yes, gently. NSW Health’s dosage chart gives 0.8 kg of bicarb to take 50 kL from pH 7.0 to 7.5, and says overdosing will not raise pH past 8.3. It raises alkalinity too, about 9.5 ppm for that dose by our arithmetic.

Does soda ash raise alkalinity?

Yes. Queensland Health says raising pH with soda ash or bicarb also increases total alkalinity. By our arithmetic, each 100 g of soda ash adds about 1.9 ppm in a 50,000 litre pool. One retailer’s listing says its soda ash does not affect alkalinity; the chemistry and the health department say otherwise.

What should my pool pH be?

SA Health says 7.2 to 7.6 for a home pool; HealthyWA says 7.2 to 7.8 with 7.5 ideal. NSW Health says below 7.2 causes bather discomfort and corrosion of pool equipment.

Sources

General information only, current at 2026-10-04. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.