Water Chemistry /
How to Get Free Chlorine Up in a Pool
To raise free chlorine, test the water first, remove debris, confirm circulation, and add sanitizer only as directed on the label and manual.
Archive date: this article was written for PoolSkimmer on Oct 23, 2026 and given the earlier archive date of Mar 7, 2026 so the blog reads as an organized archive. It was not published on that date.
Raising free chlorine: where to begin
The first step in getting free chlorine up is a good test of the pool water. From there, one must identify what is depleting it so fast. Debris, algae, a heavy bather load or inadequate circulation will all cause free chlorine to drop. The prudent course of action is to remedy the root cause and then put in sanitizer as the product label dictates.
The case for low free chlorine
As the active sanitizer in any swimming pool, free chlorine is what stands between the water and bacteria or algae. When levels are low, that protection is wanting. There are a number of usual suspects:
- Organic matter like leaves and dirt
- A clogged filter or skimmer basket in need of a wash
- Insufficient pump power
- Algae on the fixtures, walls or floor
- Contamination from rain or a lot of swimmers
- Water chemistry that renders the chlorine ineffective
Hayward’s approach to maintenance is to skim, brush, vacuum and run the pump with an eye on the filter; proper debris removal and circulation make for better pool care.
A safe way to increase levels
There is no need to guess when raising free chlorine. Follow this order of operations:
1. Shut off the pump. Do not put your hand into operating suction equipment before you open the skimmer basket. 2. Clear out the visible stuff. Skim the top and vacuum anything that has settled. 3. Service the skimmer and filter. Restricted flow means the chlorine will not be well distributed. 4. Take another reading. This will show if the loss was due to a circulation problem or contamination. 5. Apply the chlorine per the label. Whether it is tablets, granules or liquid, stick to the instructions in the manual for your particular sanitizer. 6. Let the pump do its work. You want moving water to spread the sanitizer about the pool.
Why won’t the level go up?
What appears to be a lack of chlorine can be a matter of demand. Ongoing contamination can have a pool burning through sanitizer in short order, and the numbers will fall again after treatment.
It is easy to make errors such as putting in chlorine prior to a cleaning, or running the pump less than the pool requires. One should also retest once the cleanup is done. And check the chemistry; if the pH or cyanuric acid are not within range, maintaining free chlorine becomes an uphill battle. In either case, the test kit and chemical label are your guide.
Time to call in a pro
If you have cleaned and checked the circulation but free chlorine remains stubbornly low, or the water will not clear, it is time to contact a qualified pool professional. The same applies if you see signs of an algae bloom or suspect something is amiss with the pump or filter.
Seek assistance without delay for cloudy water that will not budge, a filter that clogs repeatedly, or any electrical fault in the vicinity of the pool equipment. Under no circumstances should one swim in unsafe water or in the presence of an electrical issue.
In the end
Testing, debris removal and a clean skimmer and filter are the way to restore free chlorine, followed by adding the chemical in strict accordance with the label. Should the level still not hold, you are likely looking at an equipment issue or contamination that requires a professional’s eye.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)