---
title: "Check Valves: Why Every Carb Stone Needs One (and Ours Is Serviceable)"
url: https://getfizzwizz.com/check-valves/
date: 2026-10-05T22:01:15+00:00
modified: 2026-10-06T11:57:48+00:00
lang: en_US
---

# Check Valves: Why Every Carb Stone Needs One (and Ours Is Serviceable)

## The non-negotiable

Every carbonation stone should have a check valve. Full stop. It stops tank contents flowing backward into your gas line.

## Orientation matters more than you think

The valve end should point **vertically upward**, for two reasons:

1. **Mechanical.** Sticking out horizontally puts fittings far from the tank wall, where forklifts, hoses and elbows knock them. Keep it close and upright.
2. **Fluid-gas separation.** In a horizontal run, beer can flow along the bottom of the pipe while gas flows across the top. The check valve then sees both and starts to leak. Vertical means the valve sees one or the other, never a mix.

On the WizzStone-Combo, the upright end carries both the check valve and an isolation valve. See the [WizzStone-Combo assembly guide](/wizzstone-combo-assembly/).

## Zero crack pressure, duckbill design

Our check valve uses a **duckbill valve** with effectively **zero crack pressure** (the pressure needed to open it). That matters because carbonation is a low-pressure environment: the valve must open freely at working pressure but still seal against backward flow.

## Servicing

After a couple of years, duckbill check valves start to seep. Ours are designed to be serviced rather than replaced: undo the valve body with a wrench, swap in a new duckbill, add a little **food-grade nut lock** to the thread, and tighten until it stops and the parts line up. That stop is the correct tension.

**Need parts?** [Replacement duckbill valves](https://www.brewwizz.com/products/duckbill-valve) (pack of 10) and complete [carbonation stone check valves](https://www.brewwizz.com/products/carbonation-stone-check-valve) are available at brewwizz.com, or email [info@brewwizz.com](mailto:info@brewwizz.com) for ordering information.