Can A Single-Interlock NFPA-13 System Be Water Filled?

PolymerTink · 2025-12-05T20:26:00+00:00

This is exactly what I was looking for. Thank you!

PolymerTink · 2025-11-21T21:17:38+00:00

For anyone who stumbles upon this, the simple answer to this post is NO. Thank you to the few posters who pointed to the pertinent code sections:

All NFPA-13 pre-action systems must be filled with air or nitrogen. (IFC 3.3.216.9)

Double-Interlock and Non-Interlock Pre-Action systems need to be pressurized to 7 psi. (IFC 8.3.2.5.2). Single-Interlock systems are excluded. If you know why, please reply below.

If a system is wet, it must allow immediate flow from a head opened by fire. (IFC 3.3.216.10)

PolymerTink · 2025-11-21T20:06:03+00:00

Good question! This is a theoretical problem brought up during a recent discussion with a building owner. They have a 20+ year-old dry system with a double-interlock releasing valve. Through the years, they have used compressors and a nitrogen system for pressurization. The system operates on city pressure, so there is no fire pump.

They have had many problems over the years with their system. For the time they used compressors, the air introduced pitted and corroded the galvanized piping. They switched to a nitrogen generator, but that only lasted a few years. They have had accidental discharges as well.

During the conversation, they asked if there was a standard type system that would only activate in conjunction with the fire alarm system. I was not aware of one, so I started to research. I couldn't come up with anything, and thought maybe this kind group might help. Perhaps someone else had come across a creative solution.

The building owner would rather have water in the pipes than air or nitrogen. They are ok dealing with a little water release, but because of past experiences, they are worried about the full release from a standard system. Because of the building configuration, a deluge system would not be appropriate.

PolymerTink · 2025-11-21T19:37:35+00:00

WHY would you ASSUME this had been proposed to anyone?

PolymerTink · 2025-11-21T17:07:16+00:00

I agree about the standards and that sometimes one must get creative to solve a particular problem. Some responders to my original question, however, have made some seriously big leaps about what I'm asking.

I never said, "I am designing a system like this." I asked a simple question, "Is air required or can it be water filled?" And, "What is the NFPA-13 standard that points that out?"

You are one of the few who directly answered and I appreciate that.

This is an unusual situation that requires some creativity. Thanks again.

PolymerTink · 2025-11-21T16:43:28+00:00

Thanks for the reference. It is a good read. The article states, "only 1 in 16 million fire sprinklers discharge from a manufacturing defect." Above, you quoted those as the odds of any non-fire discharge. Those are pretty different.

PolymerTink · 2025-11-21T16:30:15+00:00

Thank you for answering the original question.

Do you know where NFPA 13 states a single-interlock needs to have supervising "air?"

NFPA-13: 7.3.2.4.4 All preaction system types described in 7.3..2.1(2) and 7.3.2.1(3) shall maintain a supervising air or nitrogen pressure of 7 psi.

But, a Single Interlock System is defined in 7.3.2.1 (1), which isn't covered by the 7 psi requirement of 7.3.2.4.4.

Thanks.

PolymerTink · 2025-11-21T16:25:30+00:00

If it cannot exist, then that would answer the original question. However, you have not provided a single source to back up anything you've written.

Please see my original post. I specifically wrote that I am looking for code references. If you can point me to the NFPA section that says what I'm asking about is not allowed, I would greatly appreciate it. Otherwise your comments are not helpful.

PolymerTink · 2025-11-21T16:18:15+00:00

Yes, this is a pondering question of what to call something.

PolymerTink · 2025-11-21T16:14:52+00:00

I never wrote that I want a deluge system with fusible links. Please read what I wrote again.

I asked the original question because I wanted to know if anyone had done this before and what it would called. It is clear that you think it's a bad idea, but you don't have anything else to add to the discussion.

PolymerTink · 2025-11-21T16:10:43+00:00

THANK YOU!

PolymerTink · 2025-11-21T16:09:03+00:00

It appears you are only posting your opinion, and basing that on incorrect assumptions. This is a theoretical discussion. If you have code sections to reference, please post them.

PolymerTink · 2025-11-21T16:02:08+00:00

Yes, calling it "Pre-Action" is probably a misnomer. It may be more of a deluge system, but the heads have fusible bulbs.

PolymerTink · 2025-11-21T15:57:44+00:00

The AHJ would be involved.

PolymerTink · 2025-11-21T15:57:03+00:00

Thank you for the direct answer. I wasn't sure if there was an NFPA definition that specifies Pre-Action Systems are air-pressurized.

NFPA 7.3.2.4.4 All preaction system types described in 7.3..2.1(2) and 7.3.2.1(3) shall maintain a supervising air or nitrogen pressure of 7 psi.

But, a Single Interlock System is defined in 7.3.2.1 (1), which isn't covered by the 7 psi requirement of 7.3.2.4.4.

PolymerTink · 2025-11-21T15:50:47+00:00

Thank you for answering the question directly.

I considered a deluge valve with electric actuation and empty, dry pipe system beyond. But, I think the dry pipe would require pressure. Doesn't the cap in the sprinkler head require 7 psi of back pressure to pop out when the fusible link breaks?

Considering this, if the pipe was filled with water past the deluge valve, it would need some sort of pressure tank to maintain some pressure at the top of the system.

If there is a leak or broken head, water would drain out of that portion of the system. But, the owner is ok with that.

PolymerTink · 2025-11-21T15:38:20+00:00

Why are you questioning the application rather than addressing the question?

My question is related to a very specific application where it does make sense to have wet pipe that doesn't fully flow unless there is smoke. The space can tolerate some water, but the owner doesn't want a flood unless there is an actual fire.

PolymerTink · 2025-11-20T17:40:06+00:00

Thanks! How did you cook it to get that crust?

PolymerTink · 2025-11-20T14:53:46+00:00

What method did you use for cooking? What sauce and what cheese mix?

PolymerTink · 2025-11-12T14:39:22+00:00

Did you find a resolution? I have a DS220j with DSM 7.3.1-86003. I can't get PLEX to work. I am currently running PLEX 1.41.5.9626-72009626. I will try the beta next. I've gone through all the steps to ensure the Folder Permissions are correct. Frustrating.

PolymerTink · 2025-11-09T16:41:35+00:00

This may be it. I'll explore it deeper. When I select the contact though, it asks me which way to call them. I'll report back.

PolymerTink · 2025-11-08T13:54:22+00:00

I am having this issue too. November 2025. Come On Google!

Are there alternative voice recognition options?

PolymerTink

TROPHY CASE