How does a Vacuum Breaker Actually Work To Prevent Contaminated Fresh Water?

Updated 08/03/2025 | Published 05/01/2019

Question:

This looks like a replacement for the unit in my trailer but I dont understand how it would be possible for the black water flush to possibly contaminate the fresh water system as I have 2 separate hose connections and use 2 separate hoses. Can you explain please?

asked by: Marven

Expert Reply:

A vacuum breaker like the Replacement Check Valve/Vacuum Breaker for Factory RV Tank Flushing Systems - 1/2" MPT # A10-3050 is used on a toilet flush valve to prevent water from being siphoned backward into the drinking water system. It doesn't matter if different hoses are used as the water can be siphoned from one area to another if not protected. If not used a toilet tank or even an overfull toilet could possibly be sucked back into the fresh water tank. Even though it would be an extremely rare possibility it is most definitely not worth the risk.

A check valve controls flow but is not absolute against backflow. A vacuum breaker is actually more of a backflow preventer completely protecting your fresh potable water. The # A10-3050 is designed to work as both.

expert reply by: Jason S

Warpness K.

7/20/2024

I have an under carriage leak when using sani flush 2012 24 ft model21 swbe

Paul J.

8/3/2025

Hello Jason, I just read your reply here: Check Valve/Vacuum Breaker for Factory RV Tank Flushing Systems - 1/2" MPT # A10-3050 is used on a toilet flush valve to prevent water from being siphoned backward into the drinking water system. It doesn't matter if different hoses are used as the water can be siphoned from one area to another if not protected. If not used a toilet tank or even an overfull toilet could possibly be sucked back into the fresh water tank. It seems impossible for the toilet or any black tank to be siphoned backward into the drinking water system, because the black tank and toilet do not have a line to drinking water. The black tank and toilet are isolated from anf drinking H20 .. This Check Valve/Vacuum Breaker for Factory RV Tank Flushing System is from outside the rv connected to outside H20 sorce to black tank . Thats it , there is no connection to rv drinking H20 tank or faucets Could you please explain? Thank you