Water Chemistry /
How to Bring Up Alkalinity in a Pool
Low alkalinity can make pool water unstable, letting pH swing and increasing corrosion risk. Learn the safe way to raise alkalinity and when to call a pro.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Jan 10, 2026 so the blog reads as an organized archive. It was not published on that date.
The effect of low alkalinity on a pool When total alkalinity is low, the water in a pool becomes less stable and the pH can be prone to rapid shifts. If one does not address it, the water will be more corrosive and difficult to balance, putting stress on surfaces and equipment while becoming an irritant for those in the water. For most pool owners, this is a maintenance headache since pH and alkalinity have a habit of moving in tandem.
Raising alkalinity safely To put some stability back in the water, the standard approach is to apply a sodium bicarbonate or other alkalinity increaser that is meant for pool use. One should test the water first and then add only what the product instructions say is permissible, adhering to both the chemical label and the equipment manual.
There are a few safety rules to observe: - Put on appropriate PPE like gloves and eye protection. - Do not mix any chemicals. - Shut off the pump if you need to get at the skimmer basket. - Refrain from pouring chemicals into the skimmer unless the manual and label give you the go ahead.
Diagnosing the problem Rather than make a guess, it is better to work through a simple process before treating the pool:
1. Run a sample test with a good quality kit. 2. Verify the total alkalinity is the issue and not merely the pH. 3. See if the pH is out of range as well; the two influence one another. 4. Give the skimmer, filter and overall circulation a once over per the manual to ensure they are in order. 5. Confirm the system is circulating so the water will mix after you treat it.
Any debris or poor flow can be an obstacle to keeping alkalinity where it should be.
Baking soda: pH or alkalinity? While baking soda is the go to for raising alkalinity, it has an effect on pH too. They are related but distinct. An increase in alkalinity might push the pH up a bit, so let the water circulate and settle before retesting. It is unwise to try and put right everything in one go without checking your work. Should both be off, let the test results or a pro tell you which to tackle first.
Pitfalls to steer clear of Some of the more frequent errors are adding product without a test, using something not for pools, or not heeding the manufacturer. Retesting before the water has had time to mix is another. And do not attempt to correct a pattern of low alkalinity without getting to the root of it. Also, leave electrical repairs to someone else and do not use live suction on baskets or debris.
When to put in a call If the pH is hard to control or the alkalinity continues to fall no matter what you do, it is time to seek assistance. The same goes if the water is cloudy, has an odd smell or feel post treatment, or if you think there is a leak or equipment damage. A qualified professional can also advise you on whether to adjust the pH or alkalinity first when in doubt.
The objective You want stable water, not just a better reading on a strip. Low alkalinity means the pH can drift and the water can turn corrosive, making routine care a chore. The way to handle it is to test, follow the manual, let the water run and then retest before doing anything else.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)