---
title: "What Is Free chlorine? Pool Glossary | Marina Pool Services"
description: "Free chlorine is the chlorine in pool water that is still active and ready to kill germs and algae right now."
url: https://marinapool.multisites.ai/glossary/free-chlorine
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Water chemistry

# Free chlorine

Free chlorine is the chlorine in pool water that is still active and ready to kill germs and algae right now.

Free chlorine is the number that tells you if your pool is safe today. A test that shows zero means the water has no protection left. Algae can bloom within days in North Texas heat.

CDC guidance for public pools sets a minimum free chlorine level of 1 ppm (parts per million). Backyard pools in strong sun often need more care to hold that level, because sunlight burns chlorine off fast. Test often, and read the label on your chlorine product. If free chlorine keeps falling, check your [cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid) and look for rising [combined chlorine](https://marinapool.multisites.ai/glossary/combined-chlorine).

[Marina can helpPool Maintenance Services](https://marinapool.multisites.ai/our-services/pool-maintenance-services)

## Related terms

-   [Combined chlorine](https://marinapool.multisites.ai/glossary/combined-chlorine)
-   [Total chlorine](https://marinapool.multisites.ai/glossary/total-chlorine)
-   [Cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid)
-   [Sanitizer](https://marinapool.multisites.ai/glossary/sanitizer)

## Sources

1.  [CDC Healthy Swimming: Operating and Managing Public Pools, Hot Tubs and Splash Pads](https://www.cdc.gov/healthy-swimming/toolkit/operating-public-pools-hot-tubs-and-splash-pads.html)

## Need a hand with your pool?

Call or text and tell us what your pool needs. Estimates are free for qualifying services, and same-day estimates are possible when the schedule allows.

[Call (817) 896-1120](tel:+1-817-896-1120)[Get a quote](https://marinapool.multisites.ai/contact)

![A pool technician working on an equipment pad](https://marinapool.multisites.ai/_astro/technician-equipment-pad.BW5xZMNY_Zum1K5.webp)