How much muriatic acid for a 50,000 litre pool?
The amount that takes a 50,000 litre pool down to pH 7.5 at 100 ppm alkalinity, for each acid strength on the shelf.
To bring pH from 7.8 down to 7.5 in 50,000 litres
↳ Also lowers total alkalinity by ~3 ppm.
Change the volume or the readings and it recalculates.
Dose table for 50,000 litres
| Current pH | Muriatic acid 31.45% | Muriatic acid 14.5% | Dry acid |
|---|---|---|---|
| 7.6 | 140 mL | 330 mL | 180 g |
| 7.7 | 253 mL | 596 mL | 326 g |
| 7.8 | 345 mL | 812 mL | 445 g |
| 7.9 | 421 mL | 991 mL | 543 g |
| 8.0 | 485 mL | 1.14 L | 625 g |
| 8.2 | 590 mL | 1.39 L | 760 g |
Alkalinity decides how much acid it takes
How much acid a pH correction takes depends on alkalinity as much as on pH, because alkalinity is the buffer resisting the change. A pool sitting at 150 ppm needs far more acid than the 100 ppm assumed here. Acid also lowers both readings together, which is why the standard fix for high pH and high alkalinity is acid plus aeration rather than one product for each.
Dosing a 50,000 litre pool
At 50,000 litres a full correction is a lot of product at once. Spread it across the deep end, run the pump through the whole dose, and test only after a full turnover. Big pools also stratify, so one sample from one corner is not the pool.
Safety
- Pour acid slowly into the deep end with the pump running, never into a skimmer.
- Never mix acid with chlorine of any kind, in the pool or in a bucket.
- Add to the deep end with the pump running. Never mix with chlorine, which produces toxic gas.
Frequently asked questions
How much acid lowers pH in a 50,000 litre pool?
345 mL of 31.45% muriatic acid takes a 50,000 litre pool from pH 7.8 to 7.5 at 100 ppm alkalinity. A higher alkalinity reading needs proportionally more.
Is dry acid the same thing?
Sodium bisulfate does the same job as a powder, which is easier to carry and store. It leaves sulfates behind, so pools that are never drained build them up over years.
Why does my pH keep climbing back?
Carbon dioxide leaving the water pushes pH up, and aeration speeds it up: fountains, waterfalls and salt cells all do it. Lowering alkalinity is what actually slows the climb.
How this is worked out
Every number here comes from the same engine as the DoseMyPool app and the calculator above, run at 50,000 litres. Amounts are estimates: product strengths vary, so follow the label on the bottle you own. See the full method
Other chemicals for 50,000 litres
Other pool volumes
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