pH plus calculator: how much to raise your pool’s pH?
A low pH is corrected with pH plus (sodium carbonate). The dose depends on volume, the gap to close and your product’s concentration. Enter your values for an estimate — after checking the total alkalinity.
Correct the total alkalinity (TAC) before touching the pH. Alkalinity is what keeps the pH stable. Until it is in the right range (roughly 80 to 120 mg/L), adjusting the pH is pointless: it will fall back after every addition and you will waste product. So check the alkalinity first, correct it if needed, and only then use this calculator.
Result
pH plus to add (indicative)2kg
The alkalinity must have been corrected beforehand (see the warning above), otherwise the pH will fall back.
Dose based on your product’s stated value. Add in small amounts, with filtration running, and retest before any further addition.
How this calculation works
This calculation is based on the dosing figure stated by pH plus (sodium carbonate) manufacturers:
Grams of pH plus = your product’s dose × Volume (m³) × pH gap, where the "dose" is the amount, per 10 m³, that raises the pH by 0.1.
That dose is about 100 g for a standard pH plus, but it varies from one brand to another: that is why it is editable above. Refer to your product label and correct the value if it differs. The pH is also a logarithmic scale, buffered by alkalinity: no formula is exact for every case. Always adjust gradually and retest. And remember: without correct alkalinity first, the pH will not stabilise.
Reference for a standard pH plus (sodium carbonate), by volume:
| Volume | +0.1 pH | +0.2 pH |
|---|---|---|
| 20 m³ | 200 g | 400 g |
| 30 m³ | 300 g | 600 g |
| 40 m³ | 400 g | 800 g |
| 50 m³ | 500 g | 1 kg |
| 60 m³ | 600 g | 1.2 kg |
Set your product’s dose above if it differs (the value varies by brand).
Frequently asked questions
How much pH plus to raise the pH?
As a rough figure, about 100 g of standard pH plus per 10 m³ raises the pH by roughly 0.1. This dose varies by brand: check your product label and enter the value in the calculator. It is an estimate, to adjust in small amounts.
Why check the alkalinity before the pH?
Total alkalinity is the water’s buffering power: it is what stabilises the pH. If it is too low (under 80 mg/L), the pH becomes unstable and falls back after each addition. So the alkalinity is corrected first.
Can I use baking soda instead?
Baking soda mainly raises alkalinity and only slightly the pH; sodium carbonate (pH plus) acts on the pH. They are two products with different effects: use the one suited to the correction you need.