How much baking soda to raise pool or hot tub alkalinity — or acid to lower it. Estimate your dose for 80–120 ppm in seconds. Free, no signup, gallons + metric.
Enter your pool volume, your measured Total Alkalinity (TA) in ppm, and your target. Most pools run best at 80–120 ppm; saltwater pools often aim a touch lower, around 60–80 ppm, because the chlorine generator continually pushes pH upward and a lower TA tempers that rise. Test TA and pH together, because the two interact: alkalinity is the reservoir that absorbs acid and resists pH swings, so you generally set alkalinity into range first and let pH settle afterward. To raise TA, the calculator assumes sodium bicarbonate (common baking soda), which lifts alkalinity strongly while barely touching pH. To lower TA, it uses an acid such as muriatic acid, the same chemical used for pH, which is why lowering alkalinity and pH are linked operations. Note where your TA reading sits relative to pH: if pH is also low, raising alkalinity will pull pH up as a side effect, so plan the sequence rather than chasing both numbers at once.
To raise alkalinity, the working figure is about 1.4 lb of sodium bicarbonate per 10,000 gallons to raise TA by 10 ppm. Worked example: a 15,000-gallon pool at 60 ppm, target 100 ppm, needs a 40 ppm rise. That is 4 × 1.4 lb × 1.5 (the volume factor) = 8.4 lb of baking soda — add it in two or three rounds, not all at once. In metric, raising 50,000 liters by 10 ppm takes roughly 0.85 kg of sodium bicarbonate, so a 40 ppm rise needs about 3.4 kg. Lowering alkalinity uses acid: roughly 0.8 quart (about 25 fl oz) of muriatic acid (31.45%) per 10,000 gallons drops TA by about 10 ppm, though this also lowers pH, which you then re-raise by aerating. Always recalculate from a fresh test after each addition rather than trusting one upfront dose.
Alkalinity is the shock absorber for pH: when TA is too low the pH 'bounces' — swinging wildly with every rain shower, chlorine dose, or splash of acid — and you will never hold a stable reading. When TA is too high, pH locks high and resists every correction, breeding cloudy water and scale. Both extremes waste chemicals and frustrate water balance, so getting alkalinity right first makes every later adjustment easier. Add baking soda by broadcasting it slowly across the deep end with the pump running, and avoid dumping a whole bag in one spot where it can cloud the water or sink undissolved. Wait at least 6 hours, ideally overnight, for it to circulate fully before retesting, because an early reading will look low. Lowering alkalinity with acid takes patience: add slowly at a return jet, never mix acid with chlorine, and aerate afterward to lift pH back without re-raising TA. Retest TA and pH together the next day.
For most pools, 80-120 ppm is ideal. For saltwater pools, a slightly lower range of 60-80 ppm is often recommended to help manage pH rise. Your chlorine source also shifts the sweet spot inside that band: acidic trichlor tablets are easier to buffer near the top (100-120 ppm), while liquid chlorine and cal-hypo pools usually hold steadiest in the lower half (80-100 ppm).
Common baking soda (sodium bicarbonate) is the most cost-effective and easiest way to raise Total Alkalinity without significantly affecting pH. Aim for the middle of the 80-120 ppm range rather than the very top — overshooting makes pH climb stubbornly later, and bringing TA back down takes acid and patience.
To lower Total Alkalinity, add muriatic acid (or dry acid). Pour it slowly in front of a return jet with the pump running, then let the water circulate; this lowers pH too, so afterward aerate the water to bring pH back up while the alkalinity stays down. Make the change in stages and retest. As a sizing guide, about 25.6 fl oz (0.8 quart) of 31.45% muriatic acid per 10,000 gallons lowers TA by roughly 10 ppm — the calculator above scales that to your pool volume and target drop.
Adjust Total Alkalinity first, then pH. Alkalinity acts as a buffer for pH, so getting it into the 80-120 ppm range first makes pH far easier to set and keeps it from drifting. If you chase pH while alkalinity is off, the pH will simply bounce back.
High Total Alkalinity (above about 180 ppm) makes pH stubborn and hard to lower, often leaves the water cloudy, and encourages calcium scale on surfaces and equipment. Lower it gradually with muriatic acid, then re-aerate to recover pH. As a worked example, taking a 15,000-gallon pool from 160 down to 120 ppm calls for roughly 154 fl oz (about 1.2 gallons) of 31.45% muriatic acid — split over several days, never in one dose.
If your Alkalinity is too low, the water loses its buffering capacity, causing the pH to swing wildly with every small chemical addition or rain event. Test TA whenever pH will not hold steady: a reading below 80 ppm means the carbonate buffer is depleted, and restoring the 80-120 ppm range usually settles pH within a day or two.
As a rule of thumb, about 1.4 lb of baking soda (sodium bicarbonate) per 10,000 gallons raises Total Alkalinity by roughly 10 ppm — in metric, about 0.85 kg per 50,000 liters. Rather than estimating, enter your pool volume and current and target TA above and the calculator returns the exact amount; then add it in two or three stages with the pump running and retest after a few hours.
Mostly alkalinity. Baking soda (sodium bicarbonate) raises Total Alkalinity strongly while nudging pH up only slightly, which is why it is the right product when TA is low but pH is already close to range. If both readings are low, raise alkalinity with baking soda first, retest, then close any remaining pH gap with soda ash (sodium carbonate) or by aerating the water. Using soda ash for the whole job instead would push TA far past its target.
Yes — products sold as alkalinity increaser or 'Alkalinity Up' are sodium bicarbonate, the same compound as plain baking soda from the grocery store, which often costs much less per pound. The dosing is identical either way: about 1.4 lb per 10,000 gallons raises Total Alkalinity by roughly 10 ppm. Enter your pool volume and TA readings above and the calculator sizes the dose for either product; just check that the label lists only sodium bicarbonate.