---
title: "What Is Chlorine demand? Pool Glossary | Marina Pool Services"
description: "Chlorine demand is the amount of chlorine the water uses up before any is left to sanitize. Plain-English pool glossary from Marina Pool Services in Grapevine..."
url: https://marinapool.multisites.ai/glossary/chlorine-demand
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Water chemistry

# Chlorine demand

Chlorine demand is the amount of chlorine the water uses up before any is left to sanitize.

When water has a lot of algae, leaves, sweat, or other waste, chlorine reacts with all of it first. That amount is the chlorine demand. Until it is met, your test will show little or no [free chlorine](https://marinapool.multisites.ai/glossary/free-chlorine).

This is why a green pool can swallow a big dose and still test at zero. The fix is to keep adding chlorine in steps and brushing until the reading holds overnight. Check [cyanuric acid](https://marinapool.multisites.ai/glossary/cyanuric-acid) and [pH](https://marinapool.multisites.ai/glossary/ph) while you do, because both change how well chlorine works. High demand that keeps coming back points to a deeper issue.

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

## Related terms

-   [Free chlorine](https://marinapool.multisites.ai/glossary/free-chlorine)
-   [Shock](https://marinapool.multisites.ai/glossary/shock)
-   [Green algae](https://marinapool.multisites.ai/glossary/green-algae)
-   [Oxidizer](https://marinapool.multisites.ai/glossary/oxidizer)

## 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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