Fittings Need a Listed Pressure to Meet Churn?

9/3/2025

We installed UL Listed grooved fittings with a rating up to 300 psi. The churn pressure of the fire pump is reaching 355 psi. The AHJ is asking for UL Listing or FM Approval to be above this pressure.

Is it mandatory under NFPA to have a UL Listing or FM Approval for the grooved fittings to cover the churn pressure, or is up to 300 psi acceptable?

What are our options here if we have to do anything?

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7 Comments

Pete H

9/3/2025 07:42:23 am

The fittings need to be able to handle the pressure of the system, even at churn.

So if the fitting is only listed to 300 psi, you can't have 355 psi in the system. It can burst/leak/break the fitting.

Yes, NFPA does call this out.

Your options are likely a pressure regulating device or valve.

Glenn Berger

9/3/2025 08:15:30 am

I concur with Pete's responses. The use of a PRV may not be possible since a very high pressure fire pump was chosen. May need to reconsider this design.

My guess of the design conditions is that a significant high-rise building is being protected. It use to be the design procedure to provide additional fire pumps at an elevated level (with a possible water tank). This would reduce the pressure rating of the main pump(s).

Jesse

9/3/2025 08:46:09 am

Yeah, what Pete and glenn said. Defimitely don't want to temp fate there

Ken Thackery

9/3/2025 09:13:34 am

Victaulic 009V will get you 365 psi, we tested 009N in a high rise at 350psi and they leaked so we switched to the V. Change out the couplings and you will be good. It's not worth the liability or lawsuit if something fails and they find out the equipmemnt wasn't listed for that pressure.

Ryan Hinson

9/3/2025 12:59:59 pm

Churn pressure must be considered on all downstream components which will be exposed to that pressure. The manufacturer MAY have other higher working pressures. I suggest reaching out to them for such documentation... otherwise provide what the AHJ is asking for.

As an example, Gruvlok products submittals catalog states the following:
- "Pressures to 250 psi on cut or roll grooved pipe with a wall thickness of 0.25" or greater."
- "Working Pressure, End Load & Pipe End Separation Based on standard wall steel pipe with cut or roll grooves in accordance with Gruvlok specifications. See technical data section for design factors."
- "Pressure ratings of Gruvlok standard fittings conform to those of Fig. 7001 Gruvlok coupling."
~ Fig 7001 coupling states "Maximum Working Pressure Rating is for schedule 40 steel pipe. For light wall, stainless steel, aluminum and ISO pipe pressure ratings, please refer to the technical data section. Not for use on "EG" rolled or cut grooved pipe ends."

Just realized this inquiry is regarding grooved fittings after having already written my initial response below. As such, I'll just include anyways:

From a flanged fitting standpoint, the pressure rating of a given pipe/fitting component is based on the specific material from which it is made and the temperature at which the piped liquid will operate as well as the applicable ANSI/ASME fitting standard:

- The stated pressure ratings for grey/cast iron fittings are at steam temperature of 353°F per ANSI/ASME B16.1. For example, an ASTM A126 Class A cast iron fittings having ASME B16.1 Class 125 rating is rated for 125 psi at 353°F. At temperatures 150°F or less, size- and Class B compoonent-specific pressure ratings are 150 psi or higher. See Table 3-1.1 of ASME B16.1 (2020) for more information.

- For forged or cast pipe flanges and flanged fittings, ASME B16.5 (2025) Tables 2-1.1 through 2.1.19 (2-1.4C for weekest group materials), a Class 150 rated component is rated for a working pressure of 235 psi for temperatures up to 100°F.

- For Ductile iron fittings, a Class 150 rating has a rated working pressure of 250 psi at 100°F or less per ASME B16.42 (2021) Table 3-1.1C.

I suggest reaching to the fitting mfgr and asking what the 'working pressure' is for your fittings at whatever your maximum anticipated water temperature is (I would expect you are below 100°F).

I have found this document to be helpful: https://gaindustries.com/images/docs/whats-up-with-flanges-7-18-24776.pdf

Good luck!

Jack G

9/3/2025 04:24:05 pm

Manufacturers obviously “ test “ their products at higher pressures than what they get approved thru UL/FM, so they don’t get leakers at the rated pressures. Sprinkler heads at one point were tested at 500 psi for 30 seconds.
But the labeled pressure is what you need to go by.
I d take Ken’s advice and see what the fittings are rated for ( with the actual piping) and see if the couplings could give you the rating, like an 007 coupling.
A prv could be used but you would have to take into account the system design. I m thinking the system would not need the actual churn pressure.

Jack G

9/3/2025 04:34:46 pm

In the Philadelphia area I ve found that A&E s design systems with pumps as stand alone ( system design is satisfied with just the pump ) and not take into account the city pressure and flow. ( degregation of city supply with development ).
Some will spec a PLD fire pump to deal with the excess pressure however the pump is tested with the PLD feature off so the excess pressure has to be designed for ( testing) .
I don t agree with this concept but that’s what some engineers do.

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Fittings Need a Listed Pressure to Meet Churn?

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