How to raise alkalinity in a pool without raising pH
To raise total alkalinity in a concrete or fibreglass pool with the least effect on pH, use sodium bicarbonate, sold as buffer or pH buffer and the same chemical as bicarb soda from the supermarket. This page works the dose through for a 50,000 litre pool from a manufacturer’s label and from the chemistry, gives the alkalinity targets from SA Health and NSW Health, explains why soda ash is the wrong product for the job, and shows the small acid correction to make if pH does creep up, with what that acid costs you in alkalinity. A salt chlorinator, pump and filtration keep running throughout.
To raise alkalinity in a pool without raising pH much, add sodium bicarbonate (buffer, or bicarb soda). One maker’s label gives 200 g per 10,000 litres for each 10 ppm rise, so lifting a 50,000 litre pool from 60 to 100 ppm takes about 4 kg. pH still rises a little; correct it afterwards with small doses of acid.
The short answer
- Dose: 200 g of buffer per 10,000 litres raises total alkalinity about 10 ppm, on one major maker’s label. The chemistry alone gives 168 g, so the label rounds up.
- Worked example: 50,000 litres from 60 to 100 ppm takes about 4 kg on the label rate (3.36 kg by the chemistry). Add it in two or three lots, not all at once.
- Bicarb nudges pH up but cannot push it past 8.3, NSW Health says; soda ash raises pH quickly and is the wrong product when only alkalinity is low.
- Target: 60–200 mg/L for a home pool (SA Health). NSW Health’s public-pool ideal is 80–100 ppm for chlorine products that raise pH; one chlorinator maker says 80–150.
- Correcting pH afterwards costs some alkalinity: 400 ml of 32% acid for 50,000 litres at pH 7.8–8.0 removes about 8 ppm, so dose bicarb with that in mind.
| Alkalinity now → target | Rise | Buffer, maker’s label (200 g per 10 ppm per 10,000 L) | Sodium bicarbonate, chemistry (168 g per 10 ppm per 10,000 L) | If pH then reads 7.8–8.0: acid to correct, and alkalinity it removes |
|---|---|---|---|---|
| 60 → 80 ppm | 20 ppm | 2.0 kg | 1.68 kg | 400 ml of 32% acid; about 8 ppm |
| 60 → 100 ppm | 40 ppm | 4.0 kg | 3.36 kg | 400 ml of 32% acid; about 8 ppm |
| 80 → 100 ppm | 20 ppm | 2.0 kg | 1.68 kg | 400 ml of 32% acid; about 8 ppm |
| 40 → 100 ppm | 60 ppm | 6.0 kg, in three lots | 5.04 kg | 400 ml of 32% acid; about 8 ppm |
How do I raise alkalinity in my pool without affecting pH?
You cannot raise alkalinity with zero effect on pH, but sodium bicarbonate comes closest. Queensland Health’s public-pool guidelines say total alkalinity is raised ‘by adding chemicals such as bicarb soda, though adding these chemicals will also affect pH’. NSW Health’s advisory document describes bicarb as a weak alkali that raises total alkalinity and ‘gently’ raises pH, and says accidental overdosing ‘will not raise the pH to greater than 8.3’.
The alternative alkali, sodium carbonate (soda ash), is the one to avoid for this job. Queensland Health says soda ash raises pH quickly and bicarb raises it more slowly, and NSW Health’s dosage chart treats 1 kg of soda ash as doing the pH work of 2 kg of bicarb.
- Test total alkalinity and pH.
- Work out the dose (below) for your pool’s volume.
- Dissolve it in a bucket of pool water and add it with the pump and filtration running; split a large dose into two or three lots.
- Re-test both readings after a full turnover, which how long a pool pump should run works out for your pool.
- If pH has drifted above 7.6, correct it with small doses of diluted acid: about 400 ml of 32% hydrochloric acid for 50,000 litres at pH 7.8–8.0 on one maker’s label.
The quotable version: sodium bicarbonate is the alkali that raises pool alkalinity with the least effect on pH, and it cannot push pH above 8.3 on its own.
How much bicarb soda to raise alkalinity in a 50,000 litre pool
One major pool-chemical maker’s buffer label says 200 g per 10,000 litres increases total alkalinity by 10 ppm.
Worked through for 50,000 litres, 60 to 100 ppm: the rise is 40 ppm, which is four steps of 10 ppm; the volume is five lots of 10,000 litres. 200 g × 4 × 5 = 4,000 g, or 4 kg.
The chemistry as a check. Alkalinity is reported as mg/L of calcium carbonate, and the USGS method sets one milliequivalent per litre equal to 50.04 mg/L as CaCO₃. Sodium bicarbonate supplies one milliequivalent per 84 mg. So 10 mg/L of alkalinity needs 0.2 meq/L × 84 = 16.8 mg/L of bicarb, or 168 g per 10,000 litres. For the example pool that is 3.36 kg. The label’s 200 g is about 19% above the chemistry, which gives a margin; start with the lower figure if you would rather approach the target from below.
Supermarket bicarb soda is the same chemical as pool buffer: Queensland Health names it as ‘sodium bicarbonate (bicarb soda)’. The difference is pack size, not chemistry.
For a 50,000 litre pool, each 10 ppm of alkalinity takes about 1 kg of sodium bicarbonate on the label rate, or 840 g by the chemistry.
What should total alkalinity be in a pool?
- SA Health, home pools: 60 to 200 mg/L, checked at least once a week, adjusted with sodium bicarbonate.
- NSW Health, public pools: 80 to 200 mg/L, with an ideal of 80–100 ppm for disinfectants that raise pH (liquid chlorine and calcium hypochlorite, per its Table 4.1) and 100–120 ppm for those that lower it.
- One salt chlorinator maker’s manual: 80 to 150 ppm.
Too low and the water will not hold its pH. NSW Health’s table of alkalinity problems lists pH bounce, etching of the pool surface, staining and heater failure below 60 ppm; above 200 ppm it lists pH lock and cloudy water, which why a pool goes cloudy covers.
A home pool reading under 60 mg/L of total alkalinity is below SA Health’s range and is the case that sodium bicarbonate is for.
Why is my pool alkalinity low?
Alkalinity is used up by acid, so the commonest cause is the acid you add for pH. One maker’s label says 100 ml of 32% hydrochloric acid removes 10 ppm per 10,000 litres. A 50,000 litre pool dosed with 400 ml a week loses about 8 ppm a week, or roughly 32 ppm a month, from acid alone.
- Acidic sanitisers. NSW Health lists trichlor (stabilised chlorine tablets) as lowering pH, which drives more acid use.
- Soft fill water. NSW Health notes rainwater is soft, ‘low in carbonates’; heavy rain or a rain-tank top-up dilutes alkalinity.
- Acidic mains or bore water, listed by Queensland Health as a cause of low pH.
If you are adding acid every week and buffer every month, the two are cancelling out, and the cause of the rising pH is the thing to fix. If that cause is a chlorinator or an interior, compare what a fix costs before buying more chemicals: compare pool quotes.
Common questions
How do I raise alkalinity in my pool?
Can I use baking soda to raise alkalinity in my pool?
Will bicarb soda raise my pool pH?
Should I raise alkalinity or pH first?
Sources
- SA Health: Pools at home and maintaining them (alkalinity 60–200 mg/L)
- NSW Health: Public Swimming Pool and Spa Pool Advisory Document, section 5.3.1, Tables 4.1, 5.3 and 6.1
- Queensland Health: Water quality guidelines for public aquatic facilities, December 2019, sections 6.1.1–6.1.2
- AstralPool: Buffer product label, dosage per 10,000 L (vendor-published)
- AstralPool: Hydrochloric Acid product label, alkalinity reduction per 100 ml (vendor-published)
- Davey: EcoSalt chlorinator installation and operating instructions, total alkalinity 80–150 ppm (vendor-published)
- USGS Oregon Water Science Center: Methods for alkalinity calculation (mg/L as CaCO3 per meq/L)
General information only, current at 2026-10-02. 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.
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