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Pool Owner’s Guide · Your Water
Total Alkalinity: The Steady Hand Behind pH
by Spectrum Pool Care
Alkalinity rarely gets the attention pH does, yet it’s the reason pH can stay put. Here’s what it is, the range to aim for, and how it works quietly in the background.
Total alkalinity measures the dissolved minerals, mostly bicarbonate, that can absorb acid before the pH changes. Think of it as a shock absorber. When rain, chlorine, swimmers or a waterfall push the water one way or the other, alkalinity soaks up the push so pH barely moves.
For most residential pools, the target is 80 – 120 ppm. In that range, pH stays steady and predictable, and every other adjustment is easier.
Partners
Alkalinity and pH
The buffer and the reading
pH is the reading at this moment; alkalinity is how firmly the water holds that reading. One is the needle, the other the hand that steadies it.
Order matters
Because alkalinity steadies pH, it’s set first. Adjusting pH while alkalinity is out of range is like straightening a picture on a loose nail.
When it runs low
pH becomes jumpy, changing quickly with each rain or chlorine addition, and the water can become harder on plaster and metal.
When it runs high
pH tends to creep upward and resist coming down, which can lead to cloudy water and scale along the tile line.
A Familiar Ingredient
From the Kitchen to the Pool
The usual way to raise alkalinity is sodium bicarbonate, the same compound as the baking soda in your pantry, just in pool-sized bags. It raises alkalinity with only a small effect on pH. Bringing alkalinity down is slower: a measured amount of acid followed by time and aeration, often over several visits, so the change is gradual and gentle.
What moves it: acidic chlorine tablets and acid additions slowly lower it; fresh top-off water and some shock products can nudge it up; heavy rain dilutes it.
Salt pools: often do best toward the lower end of the range, since salt cells tend to push pH upward.
From our routes: alkalinity moves slowly, so on weekly service we check it every four weeks, while pH and chlorine are tested and adjusted on every visit.
