Water Chemistry /
What Raises pH in a Pool?
Pool pH usually rises from aeration, added fill water, sunlight, and some chemicals. The key is to test first, then trace what changed in the pool.
Archive date: this article was written for PoolSkimmer on Oct 23, 2026 and given the earlier archive date of Sep 17, 2026 so the blog reads as an organized archive. It was not published on that date.
What is behind a rise in pool pH?
Put simply, the pH in a pool will go up as the water turns more basic. In most cases this is due to a combination of factors: heat from the sun, fresh fill water, aeration or the like, and the chemicals put into the system. The best way to start is to run a test on the pH and see what has changed of late.
Common culprits for high pH
There are some very practical reasons why the numbers in your pool may be climbing:
- *Aeration*: Over time, the action of fountains, waterfalls, spa spillover or even splash-out from returns can drive the pH higher.
- Top-offs: When you do a partial refill you may be adding water with its own alkalinity and pH profile.
- *Chemicals*: Soda ash is one product that will raise pH; baking soda is for alkalinity. Straying from the label when applying these can let the balance drift.
- Activity and heat: A warm pool with heavy use and good circulation will see some pH fluctuation.
How to identify the source
Rather than make an educated guess, follow a diagnostic routine:
1. Put the water through a reliable test kit or strips. 2. Make note of any recent variables – rain, new swimmers, chemical additions or running water features. 3. Consider the circulation; if it is weak the chemistry will not be as stable. 4. Do a safe inspection of the strainers and baskets (be sure to shut off the pump before going near the skimmer). 5. After the water has cycled, retest to see if the climb continues.
This will tell you whether you are dealing with a temporary blip or something more entrenched in the pool’s chemistry.
Is it the chlorine or baking soda?
Homeowners tend to mix up their chemicals. Baking soda is for raising alkalinity, not for every high pH situation. If you want to move the pH, soda ash is the usual choice. As for chlorine, it can have an effect but it is a matter of which sanitizer is being used and how. It is wiser to stick to the manufacturer’s instructions and the labels than to add chemicals by feel.
Don’t assume pH is the issue
Just because the water is cloudy or there is algae and debris does not mean the pH is at fault; it could be a matter of filtration or sanitation. One reading on the pH meter does not give the whole story on the water balance.
Why the pH won’t stay put
Should the level keep creeping up after you have balanced it, there is likely a recurring cause. Check for a fountain that is on too much, top-offs with water of a higher pH, or perhaps an overuse of certain chemicals. High total alkalinity can also make it difficult to hold a steady pH. Since the two work in tandem, a persistent drift calls for a wider review of the water balance.
Time to call in a professional?
If you are faced with a high pH that comes back no matter what, or if you have reason to believe there is an equipment or electrical fault, it is time to get some qualified assistance. The same goes for water conditions that are not safe for swimming. Never put yourself or others in harm’s way if there is an electrical issue; follow the manuals and wear the proper PPE. A pro can sort out whether the problem lies with the chemicals, the equipment or the circulation without any risk to the pool or its users.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)