Plumbing Backflow Prevention & Cross-Connection Control

Question 1

Under the IPC, what is the minimum air gap for a potable water outlet that is not affected by side walls?

Accepted Answer

Twice the diameter of the effective opening, minimum 1 inch

Answer

The IPC requires an air gap of at least twice the diameter of the effective opening, and never less than 1 inch, when no nearby walls affect it. Nearby side walls increase the requirement.

Question 2

Which backflow device is suitable for a HIGH-hazard (contaminant) connection that is under continuous pressure and subject to backpressure?

Accepted Answer

Reduced pressure principle (RPZ) assembly

Answer

An RPZ has two independent check valves with a relief valve between them that vents to atmosphere. That design protects against both backpressure and backsiphonage on high-hazard connections under continuous pressure.

Question 3

An atmospheric vacuum breaker (AVB) must NOT be installed where:

Accepted Answer

It is subjected to continuous pressure or backpressure

Answer

An AVB protects only against backsiphonage. It cannot have a shutoff valve downstream that keeps it under continuous pressure, and it cannot be exposed to backpressure.

Question 4

Backsiphonage is caused by:

Accepted Answer

Negative or reduced pressure in the supply piping

Answer

Backsiphonage happens when supply pressure drops below atmospheric, for example during a main break or heavy hydrant draw. The vacuum pulls contaminated water back into the potable system.

Question 5

A double check valve assembly is generally approved to protect against:

Accepted Answer

Low-hazard pollutants only

Answer

A double check valve assembly has no relief port, so it is limited to low-hazard (pollutant) connections. High-hazard contaminants require an RPZ or an air gap.

Plumbing Practice Test

Plumbing Practice Test

Plumbing Backflow Prevention & Cross-Connection Control