Pool Alkalinity Too High? Here Is How to Bring It Down
Updated 2026-05-21
Total alkalinity above 150 ppm causes three problems: pH that drifts high no matter what you do, white scale on tile and equipment, and cloudy water that will not clear with normal shocking. The fix is straightforward but takes patience.
Why lowering alkalinity is slow
Alkalinity acts as a buffer for pH. The same acid that lowers pH also lowers alkalinity, but the amounts are different and the order matters.
Standard approach: add acid in small doses with the pump running, then aerate (point return jets up). Aeration drives off CO2 and raises pH back up while alkalinity stays low. Repeat over several days.
Step by step
Day 1: Add muriatic acid or sodium bisulfate to drop pH to about 7.0 (lower than your target). Run the pump 4 hours.
Day 2: Turn return jets up to aerate the surface. Run the pump 8 to 12 hours. pH will rise back up naturally as CO2 leaves, but alkalinity stays lower than where it started.
Day 3: Retest. If alkalinity is still above 120 ppm, repeat the cycle.
How much acid to drop alkalinity by 10 ppm
Roughly: 1.5 lbs sodium bisulfate per 10,000 gallons lowers alkalinity by 10 ppm. Muriatic acid: 1 cup (8 fl oz) of 31.45 percent strength per 10,000 gallons does about the same.
PoolSense calculates the exact dose for your current reading and pool size.
Common mistakes
Trying to drop alkalinity in one day with a single big acid dose tanks pH and damages equipment.
Skipping the aeration step. Without aeration, pH stays low and you keep adding more acid that drops alkalinity past the target.
Ignoring fill water with naturally high alkalinity. If your tap water is 200+ ppm alkalinity, you may need to repeat every few months.
Skip the trial and error
Scan your test strip with PoolSense and get exact dosing for your pool, in seconds.
Get PoolSenseFAQ
Can I add baking soda mixed with acid?
No. Never mix pool chemicals. Adjust one parameter at a time, in separate doses, with the pump running.
How often does alkalinity need adjusting?
Once balanced, alkalinity stays stable for weeks. Heavy rain, high bather load, or frequent shock can drift it up over time.
Why does my pH keep rising after I lower alkalinity?
Aeration drives CO2 out of the water, which raises pH. This is normal and expected during the slow alkalinity reduction protocol.