NFPA CWBSP Exam - Topic 4 Question 18 Discussion

Actual exam question for NFPA's CWBSP exam

Question #: 18
Topic #: 4

[All CWBSP Questions]

A 4 in. (102 mm) nominal diameter Schedule 10 sprinkler main is to be supported from the structure utilizing a trapeze

hanger with a span of 8 ft (2.4 m). Using Schedule 40 pipe for the trapeze hanger, what is the minimum diameter pipe

that should be used?

A1.5 in. (40 mm)

B2 in. (50 mm)

C2.5 in. (65 mm)

D3 in. (75 mm)

Show Suggested Answer

Suggested Answer: B

For supporting a 4 in. Schedule 10 sprinkler main with a trapeze hanger spanning 8 ft, a Schedule 40 pipe of at least 2 in. in diameter is typically recommended. This size provides adequate strength for the span and weight of the sprinkler main.

by Glenn at Jul 04, 2025, 04:21 AM

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Lakeesha

5 months ago

Totally agree, 2.5 in. seems like the sweet spot!

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Olga

5 months ago

Definitely 2 in. for that span, anything bigger seems unnecessary.

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Madalyn

6 months ago

I think 3 in. is overkill for a trapeze hanger.

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Alverta

6 months ago

Wait, are we sure 1.5 in. can handle that load?

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Nana

6 months ago

Schedule 40 is usually stronger, so I'd go with 2.5 in.

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Abel

6 months ago

I’m leaning towards 3 inches because I remember the need for extra support over longer spans, but I’m not entirely confident.

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Tesha

7 months ago

I feel like the answer might be 2.5 inches, but I can't recall the exact calculations we did in class. It’s tricky with the different schedules.

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Marleen

7 months ago

I think we practiced a similar question where we had to calculate the support requirements based on pipe sizes. I want to say it was around 2 inches, but I could be wrong.

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Carmelina

7 months ago

I remember something about using a larger diameter for the trapeze hanger to support the load properly, but I'm not sure what the minimum should be.

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Allene

7 months ago

This seems like a tricky one. I'll need to make sure I understand the difference between Schedule 10 and Schedule 40 pipe, and how that affects the design.

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Kanisha

7 months ago

Okay, I think I can handle this. I'll start by calculating the weight of the 4-inch sprinkler main and then use that to determine the minimum diameter of the trapeze hanger pipe.

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Melissa

8 months ago

Hmm, I'm a bit unsure about how to approach this. I'll need to review my notes on pipe sizing and structural support calculations.

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Fausto

8 months ago

This looks like a straightforward structural design problem. I'll need to consider the load on the trapeze hanger and the allowable stresses in the pipe material.

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Allene

9 months ago

Is there an option for 'all of the above'? I mean, who doesn't love a good game of 'Guess the Pipe Diameter'? It's like a sprinkler version of 'The Price is Right'!

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Desiree

10 months ago

I'm going to have to go with B. 2 in. (50 mm). Anything bigger and I'd be worried about the trapeze hanger looking like a jungle gym instead of an actual support system.

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Lonny

8 months ago

I think C) 2.5 in. (65 mm) might be a safer option for extra support.

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Avery

8 months ago

I agree, B) 2 in. (50 mm) seems like the right choice for the trapeze hanger.

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Abel

10 months ago

D. 3 in. (75 mm) all the way! Go big or go home, am I right? I'd rather have a hanger that could bench-press a truck than one that's just barely holding on.

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Vanda

8 months ago

B: Yeah, I agree. It's always better to over-engineer than under-engineer when it comes to safety.

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Gracia

8 months ago

A: I think I would go with option D, 3 in. (75 mm) as well. Better safe than sorry!

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Arminda

10 months ago

I agree with Paris, C) 2.5 in. (65 mm) seems like the most appropriate choice

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Paris

10 months ago

I'm leaning towards C) 2.5 in. (65 mm) because of the span of the trapeze hanger

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Latricia

11 months ago

I disagree, I believe the correct answer is B) 2 in. (50 mm)

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Jenelle

11 months ago

Hmm, I'm leaning towards C. 2.5 in. (65 mm) just to be on the safe side. Better to have a bit of extra strength than to risk the whole system collapsing, you know?

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Annice

11 months ago

I'm pretty sure it's B. 2 in. (50 mm) seems like the right size for a trapeze hanger supporting a 4 in. (102 mm) main. Anything smaller would be too weak, and anything larger would be overkill.

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