Alkalinity calculator
Total alkalinity is the reading that decides whether your pH corrections hold or bounce back by the next stop. WHO describes it plainly: the higher the alkalinity, the more the water resists pH change — and too much of it makes pH adjustment a fight.
Total alkalinity is the buffer that stops pH bouncing. Fix it before you chase pH — the order matters more than the dose.
Add
12.3lb sodium bicarbonate
Broadcast slowly with the pump running. Bicarbonate barely moves pH, which is why it is the right tool for this job and soda ash is not.
Total alkalinity after the correction
100ppm
Why the order matters
Correct alkalinity first, pH second, sanitiser last. Do it the other way round and you spend the season chasing a pH that will not stay put, because there is nothing in the water holding it. A pool at 40 ppm TA can swing half a pH point between Tuesday and Friday on nothing more than rain and bather load.
Coming down: the column method
- Turn the pump off and let the water go still for a few minutes.
- Pour the acid dose in a slow column into the deepest point, one spot, not spread.
- Leave the water still for about half an hour so the acid works on the buffer locally.
- Run the pump, and if you have aeration, run it — that pushes pH back up while leaving alkalinity down.
- Re-test the next day. Repeat until the reading is in band; never dump the whole correction at once.
The calculator caps a single dose at 20 ppm of alkalinity and tells you how many days the correction takes.
Never mix
Acid and any chlorine product together produce chlorine gas. Different day, different end of the pool, or at minimum hours apart with the pump running between.
Worked example
| Reading | Move | Product | Days |
|---|---|---|---|
| TA 60 → 100 ppm | Up 40 ppm | 12.3 lb bicarb | 1 |
| TA 180 → 100 ppm | Down 80 ppm | 450 fl oz acid | 4 |
| TA 100, pH 8.2 | pH only | see pH tool | 1 |
All figures for a 22,000 gallon pool.