Lower total alkalinity
Into 21,100 gal of water, add
36.09lb 16.37kgHASA Dry Acid — sodium bisulfate, 93.5%. Total alkalinity from 180 ppm to 100 ppm.
Your pool
The answer, the drawings, every reading and every table on this page are worked for the values in these fields, and worked again as you type. The questions further down are answered for the example this page was published with.
Every product that does this
| Product | Add | Also moves |
|---|---|---|
| HASA Dry Acid sodium bisulfate 93.5% |
36.09 lb 16.37 kg |
pH moves it, by an amount no fetched source states |
| HASA Muriatic Acid hydrochloric acid 31.4% |
no quantity — see the label | pH moves it, by an amount no fetched source states |
The manufacturer's own dose sentence reads: 0.5 lbs for each 0.1 pH unit reduction per 20,000 gals of water. The figures above are computed from the product's strength.
In steps, if you would rather
| To reach | Add | Total added |
|---|---|---|
| 164 ppm | 7.22 lb | 7.22 lb |
| 148 ppm | 7.22 lb | 14.43 lb |
| 132 ppm | 7.22 lb | 21.65 lb |
| 116 ppm | 7.22 lb | 28.87 lb |
| 100 ppm | 7.22 lb | 36.09 lb |
Where the band comes from
| Source | Range |
|---|---|
| COMAR 10.17.01.45 A(2) conventional pool |
60–180 ppm |
| COMAR 10.17.01.45 A(2) spa or hot tub |
60–180 ppm |
Pool and spa rules are adopted and amended state by state, and most of the ranges here are written for public pools. Confirm every figure against the code your jurisdiction has adopted and against your own product label.
Always dilute acid before it goes in: ten parts water to one part acid, into the water and never the other way round. Run the pump while you add it and for an hour afterwards, then test again before you add any more.
Other adjustments
- raise Raise salt
- lower pH, and how to lower it
- raise Total alkalinity, and how to raise it
- raise pH, and how to raise it
- raise Raise free chlorine
- shock Free chlorine, and how to shock it
- raise How to raise Stabiliser
- raise Raise calcium hardness
Updated September 2026
Sources and dates
Ranges are quoted from the code named beside them, product strengths from the manufacturer's own product page, each retrieved on the date shown.
- COMAR 10.17.01.45 A(2) · https://www.law.cornell.edu/regulations/maryland/COMAR-10-17-01-45 · 2026-09-17
- HASA · https://hasa.com/pool-chemical-calculator · 2026-09-17
- HASA Dry Acid · https://hasa.com/product/dry-acid · 2026-09-17
- HASA Muriatic Acid · https://hasa.com/product/muriatic-acid · 2026-09-17