Is Feed to Remote FDC Allowed Under Building?

2/3/2023

Can the pipe from a remote FDC at the front of our building route under the building slab to connect to our fire pump room at the back of the building?

The Fire Pump Room is on the basement level.

This is for a six-story hotel with a partial basement along the back portion of the building that is open to a lower grade level in back. Here's a sketch below.

The fire marshal requires a remote FDC at the sidewalk in front of the building. Our fire pump room happens to be on the opposite side, in the back.

The most straightforward routing is below the building, but it is minimum 60' of run which certainly exceeds the 10' maximum distance allowed for the fire supply from NFPA 13.

Going above the first floor ceiling is challenging given all the interiors/ceilings, public spaces, and glass at the street front.

Given that the FDC pipe is normally-dry and not pressurized, do we have the same restrictions of 10' max below grade?

Even if not, can't say I'm thrilled about having that many joints below our building above. Thanks for your help/thoughts!

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13 Comments

chad

2/3/2023 08:14:53 am

FDC's are routinely routed outside away from the building. Under slab is outside/exterior to the building, in my opinion.

Depth, I don't see an issue personally, seismic would be the only consideration, if a consideration. Make sure there is a ball drip as well.

I can't think of any codes/standards that would prohibit it.

Anthony

2/3/2023 08:19:00 am

There are provisions in 13-16 for running pipe underground in chapter 10.

I'd be careful around footings and exterior foundations. Might be a good idea to talk with the structural and site civil people to make sure your routing won't be a problem. Also make sure any penetrations you do make in foundation are properly sleeved per their details.

2/3/2023 08:29:44 am

Agreed.

And I would add that is basically directs you to 24-16 for at lot of that. And from that:

10.4.3.2* Where approved, private fire service mains supplying
systems within the building shall be permitted to extend
more than 10 ft (3.0 m) under the building when all the requirements of 10.4.3.2.1, through 10.4.3.2.4 are met.

10.4.3.2.1 Where the piping is installed under the building, all
foundations or footers over the private fire service main shall be
arched to create a minimum of 24 in (600 mm) clearance.
10.4.3.2.2 It shall be acceptable to install the piping in covered
trenches where the trenches are accessible from within
the building.
10.4.3.2.3 All joints shall be mechanically restrained.
10.4.3.2.4 A valve shall be installed before the piping enters
under the building and within 24 in. (600 mm) of where the
piping enters the building.

Glenn Berger

2/3/2023 08:25:39 am

My recommendation is never install fire protection piping below a building. Depending where the check valve is place this pipe will see both wetted areas and dry areas and will corrode.

Installing the FDC pipe underground and around the building could be looked at in the context of NFPA 13.

Alex

2/3/2023 08:39:20 am

FDC piping is of course run underground with free standing connections. The main issue I see with yours is running under your building and the possibility of future repairs. You could always run up to the second floor to avoid complicated ceilings and drop within a column.

A few code sections to review for underground pipe:

Section 8.15.21 Dry Pipe Underground
8.15.21.1 - Where necessary to place pipe that will be under air pressure underground, the pipe shall be protected against corrosion.

Chapter 10 - Underground Requirements outline pipe material and fittings

Eric R

2/3/2023 08:44:29 am

As a NFPA 25 inspector I (and the owner) will hate you forever if in 5 or 10 years that pipe fails it's required 150psi hydrostatic test, and I have to explain to the owner that we need to tear up their floor to find out where the pipe failed.

Please don't do this.

R. Jackson link

2/3/2023 09:15:00 am

As a fire sprinkler contractor, my job is doing what is best for the building owner, both cost effective and code compliant. I would do whatever it takes to not feed the remote FDC under the building. I would NOT want to explain to the owner a few years down the road when the piping needs to be replaced for whatever reason. You can always do things the quick and easy way, or you can do things the best possible way. No matter which way you choose, it will say volumes about you as a designer, and the company you represent.

Kevin

2/5/2023 08:23:40 am

In reading the comments, our experience is that all underground to a FDC whether out in the yard or under the building slab is to be Cement Lined Ductile Iron Class 52 or greater. Mechanical joint is preferred. It seems the comments about corrison are for steel pipe underground which is never to installed undergorund.
Underground is always more expensive than overhead.
Chad has the correct code sections in NFPA 24 to follow for underground.

John Monsebroten

2/5/2023 11:59:58 am

There is language about connecting the FDC to a cross main. You may be able to avoid going underground which may or may not work for your project.

2/8/2023 10:56:09 am

It seems FD access may be driving the Fire Marshal's requirements. What are the existing site conditions? Would be curious to see overall site utility plan to fully address this issue, as many factors are considered when placing an FDC.

Franck

2/9/2023 09:36:07 am

As indicated above, I would never run a pipe under a building.
If something happens, you will be in big trouble, with a long impairment of the corresponding system.
And building settlement alone can create damages to the pipe. This is why it is indicated, as outlined by Chad, in 10.4.3.2.2 It shall be acceptable to install the piping in covered trenches where the trenches are accessible from within the building.

I had once an issue with the fire main supplying all sprinkler systems running under the building after it was extended... and the pipe broke.
They had to make temporary connections inside the building to limit the impairment by the time they could reroute the fire mains around the building after removing the pavement and redo it afterwards.
Costly and could have been avoided at the initial stage when the building was extended...

sean link

2/10/2023 07:43:24 am

I would avoid it at all cost

James Art FPE

3/2/2023 11:54:36 am

Code prohibits running pipe UNDER a building more than about 10 feet of length if needed to the riser.
There is an exception if it is in a covered trench, more likely in a. factory than an office building.

Perhaps just run the FDC pipe as underground OUTSIDE around the building to get to the back?
---------------------------------------------------------------------------
Thanks to person who added the illustration.
and in cold country esp. make sure pipe can be drained, where is required ball drip?

Is Feed to Remote FDC Allowed Under Building?

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