---
title: "What Is Chlorine lock? Pool Glossary | Marina Pool Services"
description: "Chlorine lock is a state where very high cyanuric acid makes chlorine work poorly. Plain-English pool glossary from Marina Pool Services in Grapevine, TX."
url: https://marinapool.multisites.ai/glossary/chlorine-lock
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Water chemistry

# Chlorine lock

Chlorine lock is a state where very high cyanuric acid makes chlorine work poorly.

Chlorine lock is a loose name for a real problem. When [cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid) gets too high, it ties up chlorine so it cannot kill algae fast. The test may show chlorine, yet the pool still turns cloudy or green.

The usual cause is months of [trichlor](https://marinapool.multisites.ai/glossary/trichlor) or [dichlor](https://marinapool.multisites.ai/glossary/dichlor) use. Adding more chlorine will not solve it. The fix is to test CYA and replace part of the water with fresh water. Then switch to [liquid chlorine](https://marinapool.multisites.ai/glossary/liquid-chlorine) to stop the build-up. Ask a pro to run a full test if you are unsure.

[Marina can helpAlgae Treatment](https://marinapool.multisites.ai/algae-treatment-grapevine-tx)

## Related terms

-   [Cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid)
-   [Stabilizer](https://marinapool.multisites.ai/glossary/stabilizer)
-   [Partial drain and refill](https://marinapool.multisites.ai/glossary/partial-drain-and-refill)
-   [Liquid chlorine](https://marinapool.multisites.ai/glossary/liquid-chlorine)

## 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)

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