Water Chemistry /
What Raises Alkalinity in a Pool?
Total alkalinity rises when pool water picks up bicarbonates, carbonates, or other alkaline substances. Testing and label-guided adjustments help identify the real cause.
Archive date: this article was written for PoolSkimmer on Oct 23, 2026 and given the earlier archive date of Aug 31, 2026 so the blog reads as an organized archive. It was not published on that date.
What is behind a rise in pool alkalinity? Total alkalinity will go up when there is an increase in the dissolved material that serves to buffer pH, in particular bicarbonates and carbonates. While one can attribute this to other chemical additions or fill water, the most likely culprit is the use of a product designed for the purpose of raising total alkalinity.
Common causes For the most part the sources are straightforward if not immediately apparent:
- Products to boost alkalinity, typically sodium bicarbonate
- Fill water with inherently high levels
- Mineral-rich water used for top-offs after evaporation
- Certain maintenance chemicals which alter the water balance over time
Should you find the total alkalinity climbing, it is worth looking at the water source and any recent additions. A professional test from your pool store will put to rest any doubt as to whether the change is coming from the treatment, the pool water itself or the fill.
Is pH a factor? There is a relationship between pH and alkalinity but they are not interchangeable. It is possible for a chemical to drive up pH without being responsible for the total alkalinity and vice versa. The best course is to test both figures rather than make assumptions.
A sensible approach would be to:
1. Use a good test kit or new strips to check pH and total alkalinity. 2. Go over what has been put in the pool lately, be it shock or an alkalinity increaser. 3. See if hard water has been used to top off the pool. 4. Put the result in context with the pool’s usual pattern instead of overreacting to a single test.
What won’t raise it? You will not see an increase in total alkalinity from the likes of brushing, skimming, vacuuming or emptying the basket. These are sound maintenance practices but they do not put buffering material into the water. They do have their place in that better circulation from a clean pool lends itself to more consistent testing and easier chemical work.
When to exercise caution Take care if the shift in alkalinity is accompanied by any of these:
- Water that stays cloudy despite normal circulation
- Scale forming on the tile or waterline
- pH in a state of flux
- Readings that don’t make sense following a few treatments
There is no point in guessing or mixing chemicals on a whim. Make sure to read the label and the manual for your equipment, put on the proper PPE and shut down the pump before getting into the filter or skimmer.
Time to get a professional involved? If the numbers are jumping around with every adjustment or you are left wondering if the test is right, put in a call to a qualified pool pro. The same goes for persistent scale, staining or cloudiness. An expert can be of great assistance when the pool has a history of balance issues; the problem may well be the source water or something in the past chemistry. It is far safer to have a clear diagnosis before adding anything else.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)