Water Chemistry /
How to Increase Chlorine in a Pool Safely
To raise free chlorine in a pool, test first, restore circulation, remove debris, and then add chlorine exactly as the product label and equipment manual direct.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Jan 24, 2026 so the blog reads as an organized archive. It was not published on that date.
Increasing the chlorine in your pool
The first step is to get a chlorine reading before making any additions. Should the free chlorine be on the low side, the remedy is typically to clear out debris and put some circulation into the water before you add chlorine as per the instructions in your equipment manual and on the chemical label. Under no circumstances should one swim in the pool until the water has returned to safe levels.
What to look at first
In many cases, low chlorine is merely a symptom of something else. A high chlorine demand can cause the numbers to drop in a hurry. Look for the usual suspects:
- An accumulation of leaves, insects or other contaminants
- A clogged or dirty skimmer
- Inadequate flow from the pump and filter
- Too many swimmers in the water
- Algae on the walls or floor
- Water chemistry that is out of balance, be it pH or stabilizer
When there is visible algae or the pool is cloudy or green, the chlorine will continue to fall until the root cause is dealt with.
Raising free chlorine without risk
1. Put the water to the test. With a good test kit or strips, check both total and free chlorine. If the result is not definitive, try again with a new sample. 2. Get the water moving. Start up the pump and filter to allow any new chlorine to make its way through the pool. 3. Power down for safety. Before you open the skimmer basket or do anything of the sort, turn off the pump. It is never wise to put a hand near operating suction. 4. Remove the debris. Give the pool walls a brush and vacuum if necessary; empty the skimmer basket. 5. Stick to the label. Whether you are using tablets in a floater, a feeder system, or liquid and granular forms, follow the product’s directions to the letter. There is no need to guess or combine products. 6. Check back after a while. Once the sanitizer has had time to circulate, retest.
The reason for a drop in chlorine
Certain pools will go through their supply quicker than others. You might find this is due to algae eating away at the sanitizer, a chlorinator not feeding as it should, or poor flow in the pump. Other culprits are imbalanced cyanuric acid or stabilizer, and the like. Contamination from sunscreen or heavy use can also have an effect. If proper treatment and repeated tests don’t yield a reading, it could be more than a lack of sanitizer.
Time to bring in a pro?
There is no harm in calling a qualified professional if the pool remains green or cloudy despite your efforts, or if the chlorine level refuses to hold. They should be contacted if the chlorinator or pump are not doing their job, or if you spot an electrical fault in the vicinity of the equipment. A pro will be able to assess the water flow and chemistry without the risk of damage.
Errors to steer clear of
Avoid adding chlorine on a hunch or from memory. Do not mix products or pour them together. And keep away from skimmer parts when the pump is on. If the water is not up to standard or there are electrical concerns, stay out of the pool.
For the most part, the best approach is to test, clean and circulate, then let the label be your guide. It is the surest way to avoid wasting chlorine and to have a pool that is safe to use.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)
- [Pentair U-3 skimmer manual: suction safety warnings](https://www.pentair.com/content/dam/extranet/nam/pentair-pool/pool-manuals/u-3-skimmers/395010028C.pdf)
- [SwimmingPool.com: Cleaning the skimmer basket](https://www.swimmingpool.com/maintenance/pump&filter/cleaning-the-skimmer&pump-basket)
- [CDC: Use pool chemicals safely](https://www.cdc.gov/healthy-swimming/media/pdfs/Pool-Chemical-Safety-USE-poster-p.pdf)
- [CPSC: Electrical safety in and around pools](https://www.cpsc.gov/safety-education/safety-guides/pools-and-spas/dont-swim-shocks-electrical-safety-and-around-pools)