Pool pH Minus - Sodium Bisulphate

Sodium bisulphate dry-acid pH Minus for swimming pools. The safer alternative to muriatic acid, dropping pH 0.2 per 15 g per m³ in clean granule form, no decanting and no fumes.

• Drops pH approximately 0.2 per 15 g per m³.
• Drops total alkalinity approximately 10 ppm per 15 g per m³.
• Replaces hazardous liquid hydrochloric acid with a clean granule.
• Restores chlorine effectiveness when pH has crept above 7.8.
• Stops calcium scale forming on heaters and tile lines.

Sizes and prices

• 5kg: £21.00
• 10kg: £38.00
• 25kg: £89.00

When you need it

• pH reads above 7.8 on a fresh sample.
• Total alkalinity is over 150 ppm and water has gone cloudy.
• Cal-hypo shocks have driven pH up.
• Heater elements show white scale build-up.
• Chlorine is dosing well but free chlorine reading is sluggish.

How to use

1. Test pH, alkalinity and free chlorine.
2. Calculate dose: 15 g per m³ drops pH by approximately 0.2.
3. Pre-dissolve dose in a 10 L bucket of pool water; never directly broadcast.
4. Pour solution slowly across the deep end with circulation on.
5. Run filtration 4 hours.
6. Retest pH and TA; correct in increments rather than over-dosing.

Dosing guide

Doses are starting points; always retest 4 hours after dosing. Sodium bisulphate also drops TA approximately 10 ppm per 15 g per m³, so balance pH and TA in sequence.

• For 20 m³, add 300 g to reach Drop pH 0.2.
• For 40 m³, add 600 g to reach Drop pH 0.2.
• For 60 m³, add 900 g to reach Drop pH 0.2.
• For 40 m³, add 1.2 kg to reach Drop pH 0.4.
• For 100 m³, add 1.5 kg to reach Drop pH 0.2.

How it works

Sodium bisulphate (NaHSO4) at 95% purity, the standard dry-acid pH reducer for swimming pools and process water.

Sodium bisulphate dissolves to release hydrogen ion and bisulphate, both of which react with carbonate buffer to drop pH and TA. The reaction is fast and pH change is visible within 30 minutes.

Above pH 7.8 chlorine sits as hypochlorite ion, which is 60 times less effective as a sanitiser than the hypochlorous acid form below pH 7.6. Dropping pH back into 7.2-7.6 instantly restores chlorine power.

Frequently asked questions

How much do I dose?

15 g per m³ drops pH approximately 0.2. Always pre-dissolve and retest before re-dosing.

Will it drop alkalinity?

Yes, by about 10 ppm per 15 g per m³. Adjust pH and TA in sequence rather than chasing both at once.

Can I use vinegar or lemon juice?

No. Both are organic acids that feed bacteria. Use proper dry acid only.

Pack sizes?

5 kg, 10 kg and 25 kg sacks.

How long does a pack last?

5 kg lasts a typical 40 m³ pool around 4-6 months of weekly correction.

Is it the same as muriatic acid?

Same job, much safer to handle. Sodium bisulphate is a granule; muriatic acid is fuming hydrochloric.

What is the active ingredient?

Sodium bisulphate (NaHSO4) at 95% purity.

How does it differ from hydrochloric acid?

Dry acid is a granule that dissolves to release H+ slowly; hydrochloric is a liquid that releases H+ instantly. Same end effect, very different handling risk.

Why does it drop alkalinity?

Bisulphate ion reacts with carbonate buffer; both pH and TA fall in proportion.

pH overshoot down?

Lift back with pH Plus; retest in 4 hours.

TA collapsed?

Lift TA with sodium bicarbonate first, then correct pH.

Dry acid vs liquid acid?

Dry acid is safer to store, ship and dose; liquid hydrochloric is cheaper per ppm but generates fumes and burns skin instantly.

pH Minus vs pH Plus?

pH Minus drops pH; pH Plus lifts it. Use whichever fits the test reading; never both at once.