What is a vacuum breaker check valve and why do I need it?

There are so many questions about the black tank flush system, so here is a post to help out. You or your spouse may have noticed this vacuum breaker under a sink or behind a cabinet drawer. Here is some information and some pictures to help you understand what it does.

The black tank flushing system

The black tank flushing system is a straightforward system that uses fresh water from a hose connection to flush your black tank to help clean it out.

It consists of a hose connection on your trailer, a vacuum breaker check valve, and the flush nozzle. It is typically piped using 1/2” white PEX tubing.

The vacuum breaker check valve

The vacuum breaker check valve is typically located up under the bathroom sink. If not there, then it will be in the wall of the bathroom somewhere. It may be behind the shower wall.

If you have two black tanks there will be a separate valve for each tank.

The vacuum breaker check valve acts to prevent black tank water from flowing back into the domestic water system that you are using for flushing water, and thereby contaminating it.

It is common for the valve to be installed backward, which prevents water from flowing through the flush line. It is also common for it to leak out of the top, so keep a close eye on it when flushing the black tank.

Some owners have advised that the plastic valves tend to freeze and crack in the winter. You can change out the valve to a brass vacuum breaker if you are in a cold climate.

Hope this information helps you better understand more about vacuum breakers and why they are used.

Water Line Tools

Please follow us on YouTube and other social media pages.

Thank you,

author avatar
California RV Specialists