---
title: "What Is Backflow? Pool Glossary | Marina Pool Services"
description: "Backflow is water flowing the wrong way into a clean water supply. Plain-English pool glossary from Marina Pool Services in Grapevine, TX."
url: https://marinapool.multisites.ai/glossary/backflow
publisher: Marina Pool Services
phone: +1-817-896-1120
quote: https://marinapool.multisites.ai/contact
---

Spa and safety

# Backflow

Backflow is water flowing the wrong way into a clean water supply.

A hose left under pool water or a fill line without protection can draw pool water back into the house supply. That can pull in chemicals and germs.

Keep the hose end above the water line when filling. Use a backflow preventer or vacuum breaker on hose bibs and fill lines. Cities and codes may require one. Ask a licensed plumber what your home needs. Ask your city utility whether a check is required each year.

## Related terms

-   [Fill water](https://marinapool.multisites.ai/glossary/fill-water)
-   [Automatic water leveler](https://marinapool.multisites.ai/glossary/automatic-water-leveler)
-   [Water restrictions](https://marinapool.multisites.ai/glossary/water-restrictions)

## 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)