WATER SERVICES

Vacuum breakers and backflow at hose taps

The most common backflow risk on a domestic job is not exotic. It is a garden hose left in a bucket, a pool, or a trough, with a pressure drop in the main pulling that water back into the supply. A vacuum breaker is the small, cheap fix.

What a vacuum breaker does

A vacuum breaker, or anti-siphon device, lets air into the line when the pressure drops, which breaks the siphon and stops contaminated water being drawn back up a hose into the drinking supply. It is a basic protection for outlets that a hose connects to.

The hose tap rule

A hose tap outlet is positioned above the flood level rim of any fixture, so its outlet is never sitting at or below the level of standing water. A garden hose is also never left submerged in a pool, pond, or tank while connected to the potable supply. Where those conditions cannot be guaranteed, a vacuum breaker or other backflow device handles it.

When you need more than a vacuum breaker

What to photograph

Show the device on the outlet and the hose tap position relative to any flood level rim. Elemetric keeps the shot with the job. For the full picture see the backflow prevention guide.

Common questions

What does a vacuum breaker do?

It lets air into the line when pressure drops, which breaks the siphon and stops contaminated water being drawn back up a hose into the drinking supply.

When do I need more than a vacuum breaker?

Higher-hazard connections call for a registered testable device such as an RPZ instead. Match the device to the hazard, not to convenience.

General information for licensed tradespeople, not legal or regulatory advice. The licensed plumber remains solely responsible for compliance. Refer to the current AS/NZS 3500 standards and the Building and Plumbing Commission (formerly the VBA) for authoritative requirements.