How to Raise Alkalinity in a Pool

Total alkalinity is a solid, not a guess: a weighed amount of baking soda or soda ash raises it by a figure that follows from the chemistry, the way a recipe's baking soda raises a cake rather than sitting there undecided. That is the opposite of pH, whose acid or base demand depends on how hard the alkalinity in the water is already pushing back. Settling alkalinity is the part of this job that actually has a number, and it is worth doing first, in this order.

The order

1. Test total alkalinity and pH together. You need both readings to know whether alkalinity is the only thing moving or whether pH is going to need attention once alkalinity is settled.
2. Size the dose from your own gallons. The pH and alkalinity calculator turns a current reading and a target into a weight of baking soda or soda ash, because the strength printed on different bags is not identical and a flat scoop count from a forum thread was measured in somebody else's pool.
3. Add it to the deep end with the pump running, so it dissolves and mixes rather than sitting on the bottom or clouding the shallow end.
4. Circulate for several hours, then retest, because a jump this size does not finish moving the moment the bag is empty.
5. Only then look at pH. Baking soda raises pH a little of its own accord, so a target pH chosen before alkalinity is settled is a target chosen against water that is about to move again.

Why alkalinity is worth fixing on its own

PHTA's fact sheet on alkalinity explains what a properly adjusted reading actually buys a pool: "Total alkalinity is a key parameter in the maintenance of water balance. When total alkalinity is properly adjusted, pH, swimmer comfort, sanitizer efficacy, water balance, and clarity are more easily maintained." A single number is doing several jobs at once, which is one reason it is worth treating as its own step rather than folding it into a pH correction.

Too little alkalinity leaves pH free to swing with every dose of chlorine or every rainstorm; too much of it pushes pH to drift upward on its own, largely independent of anything you add. The band this site checks a reading against is 60 to 180 ppm, MAHC 2024's figure, a public-pool code, and it is the widest published band this site could find — narrower ideals sit inside it, and which one applies depends on the sanitizer.

Two different ideal bands, by sanitizer

PHTA's fact sheet splits the ideal further by what the pool is chlorinated with. "Ideally, total alkalinity should be maintained between 80 and 100 ppm as CaCO3 where electrolytic chlorine generators, calcium hypochlorite, lithium hypochlorite, and sodium hypochlorite are used", because that group of sanitizers tends to push pH upward on its own. "Where sodium dichlor, trichlor, chlorine gas and bromine are used, the ideal range is between 100 and 120 ppm as CaCO3", because that group pulls pH down instead. A salt pool and a tablet-fed pool are aiming at two different targets for the same reading, which is why the calculator asks for a target rather than picking one for you.

What the weight actually is

PHTA's fact sheet gives the underlying figure this site's own arithmetic is checked against: "Approximately 1.5 pounds of sodium bicarbonate (100%) will raise the total alkalinity of 10,000 gallons of water by 10 ppm." The molecular weight of sodium bicarbonate gives almost exactly that same number worked from first principles, so the two agree, and the calculator's dose scales that figure to your own gallons and your own gap between reading and target rather than reprinting a fixed per-bag amount.

Handling the product

Baking soda and soda ash are both solids, sold at strengths close to pure, and they carry none of the pour-order warnings a liquid acid does — there is no concentrated liquid here that reacts badly with a splash of water. What still matters is spreading the dose: adding the whole bag in one spot, right by a return line, can cloud the water or leave a pile of undissolved powder on the bottom of a vinyl or fiberglass pool until the pump breaks it up.

Where the arithmetic picks up

The pH and alkalinity calculator is where this order turns into a number: a weight of baking soda or soda ash for your own volume and your own gap, your carbonate alkalinity once cyanuric acid is taken back out of the total alkalinity reading, and both figures checked against the published ranges. What it will not do, on either side of a move, is print a pH dose — that half of the job stays with your own test kit, described on the page about lowering pH instead.