Water Chemistry /
List of Pool Chemicals and What They Do
Pool chemicals help sanitize water, balance pH, control algae, and protect surfaces and equipment. Test first, then follow your pool manual and product labels.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Dec 3, 2025 so the blog reads as an organized archive. It was not published on that date.
Pool chemicals in the home: what is being used? Homeowners put pool chemicals to work to keep the water clean for swimming, to balance its chemistry and to act as a sanitizer. The staples are sanitizers, pH and alkalinity products, calcium hardness adjusters, stabilizer, algaecide, shock, clarifier and items for stain or scale control. It is best to run a water test before doing anything else, then adhere to the chemical labels and your pool manual.
A guide to what each chemical does Below is a rundown of the main pool products and their function:
- *Sanitizer*: For the most part this is chlorine or bromine, which puts an end to bacteria and other microorganisms in the water.
- Pool shock: Think of this as a heavy duty treatment for cloudy water or to get the pool back in shape after a storm or a lot of use. Do not guess at the quantity; read the label.
- pH increaser/decreaser: These are for getting the pH where it needs to be. Proper pH means the sanitizer can do its job and the water is more agreeable to swimmers.
- Alkalinity increaser: Used to put up total alkalinity, thereby stabilizing the pH so there are no sudden swings.
- Calcium hardness increaser: If the water is on the soft side, this will raise the calcium to spare your equipment and pool surfaces.
- Stabilizer (cyanuric acid): An aid in shielding outdoor chlorine from the sun.
- *Algaecide*: Not a substitute for a good sanitizer, but a support product to check algae.
- *Clarifier*: Allows the filter to do away with small particles by making them clump up.
- Stain and scale control: Tackles mineral and metal staining that comes with hard water.
Making the right choice There is a straightforward way to go about it:
1. Start with a test of the pool water for pH, total alkalinity and sanitizer levels. Check CYA and calcium hardness if you have to. 2. Identify the issue. Is the water clarity poor? Are you seeing green algae or scaling? 3. Make sure circulation is sound. Hayward points out that chemicals are only as effective as the pump and filter allow, so see that they are running as the manufacturer intends. 4. Put in what the manual and label say. Unless the instructions give permission, do not mix your products.
Where things go wrong Some of the more frequent errors in pool chemistry include: - Failing to test before adding anything. - Applying the wrong chemical to the situation. - Combining pool chemicals. - Letting the filter slide while the water remains cloudy. - Neglecting to brush, vacuum or clean the skimmer, leaving debris behind.
Time to call in a professional? If you have done the normal maintenance and the water is still foamy, green or cloudy, or if you are faced with persistent corrosion and staining, a qualified pro should be contacted. The same goes for when test results are confusing or the circulation system is underperforming.
When dealing with the equipment, safety is paramount. Turn off the pump before you look in the skimmer basket and have the manual at hand. Read all labels and don your protective gear. Never put a hand in operating suction or go near an outlet. And if there is an electrical problem or the water is not safe, do not swim until it has been put right.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)