Operator terms · Water
What is a vacuum breaker?
A vacuum breaker is a simple backflow prevention device that lets air into a line if the pressure drops, breaking the suction that could siphon contaminated water back into the supply. A common type screws onto a hose bibb to protect against back-siphonage.
Last reviewed 2026-08-03
How it protects the supply
If system pressure falls, water can be siphoned backward from a customer's plumbing into the main. A vacuum breaker opens to let air in when that happens, breaking the siphon so nothing is drawn back.
Where it is used
A hose bibb vacuum breaker is a common low-hazard example, protecting against a hose left in a bucket or pool. Higher-hazard connections use tested backflow assemblies instead.
Common questions
- What does a vacuum breaker do?
- It admits air to break the suction that could siphon water backward.
- Where is a simple one used?
- On a hose bibb, to prevent back-siphonage.
- Is it enough for every hazard?
- No; higher-hazard connections need tested backflow assemblies.