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Schedule 40 vs 10 for pre-action system

Jeng84

Jeng84

Industrial
Aug 9, 2024
14
Need some help decoding and/or point in the right direction for steel pipe schedule for sprinkler systems per NFPA 13. I'm looking in NFPA 13 (2022 edition) and I can't find any section that talks about when/if Im allowed Schedule 10 piping?
These are the 2 questions I'm trying to find answers to in FNPA 13:
1) For a double interlock pre-action system (charged with Nitrogen) using black steel pipe - are Schedule 10 piping allowed or does it have to be Schedule 40? Or does it depend on the pipe size and/or pressure
2) For a regular wet pipe system (using black steel pipe) - is Schedule 10 pipe allowed? or does it depend on the pipe size and/or pressure

I assumed it would be Chapter 7 (Requirements for System Components and Hardware) section 7.3 for above ground pipe or Chapter 8 (Preaction system and Deluge systems) but I can't find anything specific.
 
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Both ASTM A795 and ASTM A53 are available in schedule 10 so there is not problem specifying it. However, there are restrictions. See 7.5.1.2.

There is nothing against using schedule 10 for dry pipe systems. However, given the requirements 7.5.1.2 there may be an other schedule more desirable (i.e. 40) in case you would like to have even butts at the connections which allows complete draining in the pipework. Otherwise, schedule 10 is fine.
 
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thanks! very helpful! I also found Section 16.3.2 and 16.3.3, which I believe says the same thing you pointed out - If I want threaded fittings I have to use Schedule 30 (pipes 8" and larger) or Schedule 40 (smaller than 8")... But if Im not using threaded fittings I can use Schedule 10.
It doesn't seem like it's based on the type of sprinkler system (wet pipe vs pre-action) but just on the type of pipe and fittings
 
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Schedule 10 and 40 are allowed to be used in wet pipe, dry pipe and preaction for just about every situation. What type of fire sprinklers are you using?
 
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Jeng84 said:
Need some help decoding and/or point in the right direction for steel pipe schedule for sprinkler systems per NFPA 13. I'm looking in NFPA 13 (2022 edition) and I can't find any section that talks about when/if Im allowed Schedule 10 piping?
These are the 2 questions I'm trying to find answers to in FNPA 13:
1) For a double interlock pre-action system (charged with Nitrogen) using black steel pipe - are Schedule 10 piping allowed or does it have to be Schedule 40? Or does it depend on the pipe size and/or pressure
2) For a regular wet pipe system (using black steel pipe) - is Schedule 10 pipe allowed? or does it depend on the pipe size and/or pressure

I assumed it would be Chapter 7 (Requirements for System Components and Hardware) section 7.3 for above ground pipe or Chapter 8 (Preaction system and Deluge systems) but I can't find anything specific.
Click to expand...
n NFPA 13 (2022), steel pipe schedules are governed by Table 6.2.3.1, which specifies minimum wall thickness based on pipe size. Schedule 10 is permitted only if it meets the table’s minimum thickness for the given size (e.g., allowed for larger diameters like 8"+ where Schedule 10 meets/exceeds the thickness). For smaller sizes (e.g., ≤6"), Schedule 40 is typically required. Pressure ratings must also be verified against the system’s design pressure.

  1. Double Interlock Pre-Action: Schedule 10 is allowed if it meets Table 6.2.3.1’s thickness and pressure requirements.
  2. Wet Pipe Systems: Same criteria apply—Schedule 10 is permitted only where wall thickness and pressure ratings comply.
Check Pipe Schedule Chart for exact dimensions and cross-reference with NFPA 13 Table 6.2.3.1.

Key Sections:

  • NFPA 13 (2022): Table 6.2.3.1, Section 6.2.2 (Steel Pipe).
  • ASME B36.10M for pressure ratings.
For smaller pipes, Schedule 40 is often mandatory; Schedule 10 may work for larger sizes. Always confirm pressure compatibility.
 
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Pipes as thin as Sch 5 are used in fire sprinkler systems. Obviously you aren't going to thread anything below Sch 30. You can use Sch 10 down to 1¼" with no problem at all. Now that Victaulic makes a 1" grooved system (IGS), I don't see why you can't use 1" Sch 10.

Long gone are the days where 2" and smaller was to be Sch 40 and ≥2½" to be Sch 10. You may have reasons for your project why you want to use Sch 40 or any other schedule.
 
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Department of Defense still specs 2" and smaller be sch. 40 and anything larger than 2" may be sch. 10. Per code you may use sch. 10 in preaction systems no problem but your contract/specs may say otherwise.
 
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