BAT Material Selection & Properties 2

Question 1

Which elastomer is most commonly used for check valve discs in standard potable water backflow preventers?

Accepted Answer

Nitrile (NBR)

Answer

Nitrile (NBR) rubber is widely used for check valve discs due to its good resistance to water, oils, and typical plumbing conditions.

Question 2

Which rubber compound is preferred for backflow preventer seals in systems where chloramines are used as the primary disinfectant?

Accepted Answer

EPDM

Answer

EPDM has superior resistance to chloramines and chlorinated water compared to nitrile rubber, which degrades faster in these conditions.

Question 3

What is the primary failure mode when nitrile rubber (NBR) seals are exposed to petroleum-based fluids in a backflow assembly?

Accepted Answer

NBR swells and loses its sealing properties

Answer

NBR swells significantly when exposed to petroleum-based products, causing the seal to deform and lose the ability to create a watertight seat.

Question 4

What spring material is standard in spring-loaded check valves used in backflow prevention assemblies?

Accepted Answer

Stainless steel

Answer

Stainless steel is the standard spring material because it provides the corrosion resistance, consistent spring tension, and fatigue strength needed for reliable check valve operation.

Question 5

Galvanic corrosion within a backflow assembly is most likely to occur when:

Accepted Answer

Two dissimilar metals are in electrical contact within a conductive solution

Answer

Galvanic corrosion requires an electrochemical cell: two dissimilar metals acting as anode and cathode connected in a conductive electrolyte such as water.

(BAT) Backflow Assembly Tester Certification Practice Test

(BAT) Backflow Assembly Tester Certification Practice Test

BAT Material Selection & Properties 2