NFPA CWBSP Exam - Topic 3 Question 26 Discussion

Actual exam question for NFPA's CWBSP exam

Question #: 26
Topic #: 3

For an existing antifreeze system without a backflow prevention device, what size hole is required in the check valve separating the supply and the antifreeze?

A1/32 in. (0.79 mm)

B1/16 in. (1.59 mm)

C1/8 in. (3.17 mm)

D1/4 in. (6.35 mm)

Show Suggested Answer

Suggested Answer: A

If sprinklers are above the level of the water supply to the antifreeze system, a check valve with a 1/32 in. (0.8 mm) hole in the clapper shall be provided in the U-loop.

by Derrick at Mar 08, 2026, 07:39 PM

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Carlton

1 day ago

I thought it was 1/8 in. (3.17 mm).

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Rebecka

6 days ago

It's definitely 1/16 in. (1.59 mm).

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Camellia

11 days ago

I have a feeling that 1/4 in. is too large for a check valve in an antifreeze system, but I can't recall the exact reasoning behind it.

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Ezekiel

17 days ago

I practiced a similar question, and I recall that 1/32 in. was mentioned as a possible option, but I can't remember if it was for this specific scenario.

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Stephanie

22 days ago

I'm not entirely sure, but I feel like 1/16 in. could be the right answer since it's smaller and might prevent backflow better.

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Evangelina

27 days ago

I think the hole size might be 1/8 in. because I remember it being a common size for check valves.

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