How to lower pool pH: dose and product
To lower pool pH (when it’s above 7.6) you use a pH reducer (liquid or granular, based on sodium bisulfate or diluted hydrochloric acid). As a reference: to lower the pH by 0.2 in a 50 m³ pool you need roughly 1 L of liquid reducer or 1 kg of granular. Always measure before and after with a pH test, and never add more than half the calculated dose at once.
Paso a paso
- 1
Measure the current pH
With a test strip or colorimetric test. If it’s between 7.2 and 7.6 you’re in range — do nothing. If it’s above 7.6 it needs lowering.
- 2
Calculate the dose
Rule of thumb: 1 L of liquid reducer lowers the pH by ~0.2 in 50 m³. For 50 m³ at pH 8.0: you need to lower it by 0.4 → 2 L of reducer.
- 3
Dilute and pour slowly
NEVER pour acid straight into the pool near the skimmer or steel parts. Dilute it in a large bucket of water (acid into water, never the other way round) and pour it around the pool with the pump running.
- 4
Add only half the dose
Apply the first 50% of the calculated dose. Wait 4–6 h with the pump running and measure the pH again. If it’s still high, add the rest. Lowering the pH in stages avoids over-acidifying.
- 5
Check the alkalinity
If the pH keeps drifting (rising again every few days), the alkalinity is probably high (>120 ppm). Adjusting the alkalinity stabilises the pH in the long run.
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What is the ideal pH for a pool?▾
Between 7.2 and 7.6. Below 7.2 the water is acidic and irritates eyes and skin; above 7.6 the chlorine loses effectiveness and limescale builds up on the walls.
What happens if the pH is too high?▾
Three things: (1) chlorine stops disinfecting properly even if you add a lot, (2) limescale and deposits appear, (3) it can irritate skin and eyes when swimming.
How long does it take to lower the pH?▾
With the pump running, the reducer acts within 2–4 hours. It’s best to wait 6 h before measuring again and before adding more, so you don’t overshoot and over-acidify.
Liquid or granular reducer, which is better?▾
The liquid (diluted hydrochloric acid base) is faster and cheaper but requires caution when handling. The granular (sodium bisulfate) is more convenient and safer but more expensive per kg. For home use we recommend granular.
Sigue leyendo
How much chlorine to add to a pool? Dose table per m³
Maintenance: 200–250 g/25 m³ per week in tablets. Shock: 15–20 g/m³. Target free chlorine: 1–3 ppm.
Green pool water? How to clear it up in 24–48 hours
Green water = algae. Shock chlorine + algaecide + flocculant, in the right order. Results in 24–48 h.