Docs / How PoolHealth works
How the calculations work: pH targets and recommendations
Why the pH target in PoolHealth has an arrow, why the main view works with one acid, how our recommendations choose chemicals, and which chemicals the app supports.
The pH target and its arrow
In PoolHealth you set a pH target. In the main view the target has an arrow pointing down: it is the target for lowering the pH. By default it works with hydrochloric acid, 31–33%.
The dose it shows is calculated for this acid, and so is everything that follows from it: the expected total alkalinity (TA) after the dose and LSI new, the LSI after the planned treatment.
Further down, in the chemicals section, there is also a pH target with an arrow pointing up. It is an additional calculation: it works out the dose of a chemical that raises both the pH and the total alkalinity (TA).
Why the main view is about lowering the pH
Pool water holds more dissolved carbon dioxide than the air above it. By Henry’s law, the gas leaves the water until the two are in balance, and as it leaves, the pH rises. Aeration, such as spa jets and water features, speeds this up. Naturally, the pH of pool water drifts upwards. We take this as the basis: the main view is built around the pH target that lowers, with the arrow pointing down.
Why the acid comes first for the buffer
pH depends strongly on the buffer, the carbonate alkalinity of the water. When you add acid, it lowers the buffer first, and only then the pH. This is why the same pH target takes different amounts of acid in different pools, and why a dose has to be calculated from the alkalinity (TA) and cannot be a fixed number.
One chemical in the main view, others below
At the bottom of the main view you see the figure for the chemical that lowers the pH in the main calculation. If you use a different chemical, you can find it below, in the chemicals section, together with the additional calculation for raising the pH.
Different chemicals, different concentrations
Our calculator works with different types of chemicals and different concentrations. We added the main, basic settings. For most chemicals you can change the concentration in the settings, so the calculation matches the product you actually use. The one exception is potassium monopersulfate, which has no strength setting.
You can also track other chemicals, and how much of them you use. If you have not found the type of chemical you work with, but would really like it added, write to us at info@pool-health.com.
What is already in the app
Chemicals you can log in a visit:
- Sodium hypochlorite 12% (NaOCl), in litres
- Hydrochloric acid 31–33% (HCl), in litres
- Sodium bicarbonate (NaHCO₃), in kg
- Sodium carbonate (Na₂CO₃), in kg
- Cyanuric acid (CYA powder) (C₃H₃N₃O₃), in kg
- Calcium chloride 70% (CaCl₂), in kg
- Trichloroisocyanuric acid, trichlor (C₃Cl₃N₃O₃), in kg
- Sodium dichloroisocyanurate, dichlor (C₃Cl₂N₃NaO₃·2H₂O, dihydrate), in kg
Other chemicals you can switch on in My profile:
- Calcium hypochlorite Ca(OCl)₂, in kg. A chlorine source: it adds free chlorine and calcium hardness (CH).
- Potassium monopersulfate KHSO₅, in kg. A non-chlorine shock: it adds sulphates and lowers the total alkalinity (TA) slightly. It has no strength setting, because its sulphate and acid content are fixed.
- Sulfuric acid H₂SO₄, in litres. An acid: it adds sulphates and lowers the total alkalinity (TA).
- Sodium bisulfate NaHSO₄, in kg. A dry acid for lowering the pH: it adds sulphates and lowers the total alkalinity (TA).
- Sodium bromide NaBr, in kg. It “activates” the bromine reserve in the water.
- Bromine tablets (BCDMH) C₅H₆BrClN₂O₂, in kg. Tablets for a continuous supply of bromine.
Switch on the ones you use. They then appear in your visits, and what you add is turned into the sulphates and calcium it puts into the water. These figures are estimates from the chemistry of each compound and the concentration you set, so check the strength on your label.
Anything else. You can add a chemical of your own with a name and a unit. It then shows up in the chemical stock, in your visits and in the chemical usage.
What our recommendations are built on
Our recommendations are built around specific chemicals. We choose those whose effect on disinfection and water balance is the most stable, and which add the fewest by-products to the water.
We know that professionals may use other chemicals. That is why the system is built for everyone: you can add the chemicals you use and compare them with ours.
Why raising the pH is not part of our recommendations
Our recommendations are not built around raising the pH, and we do not recommend it. We do not use chemicals that have a low pH themselves, because they also affect the buffer, so in our practice the pH does not need raising. The calculation is there for those who use such chemicals.
This article is general information, not professional advice. Always follow product labels and the rules that apply where you live.
Spotted something outdated or inaccurate? Tell us at info@pool-health.com and we will check and correct it. Last reviewed: November 2026.