Sprinkler Pipe Run Underground After Riser?

12/9/2021

Can you run sprinkler pipe underground after the riser has entered the building?

The building we're working on is an apartment building that is being sprinklered to NFPA 13R (2016 Edition). The apartment is 4-story and has open air breezeways. There are dry sidewalls protecting the breezeways.

The owner wants to run pipe under the slab in the open air breezeways instead of providing a heated path for sprinkler pipe across the breezeway. I have strongly recommended against this, but have gotten pushback from the owner and contractor regarding this pipe arrangement.

Is this underground arrangement allowed?

I believe there are some cases where this is acceptable but not many. Thanks in advance!

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11 Comments

Alex

12/9/2021 07:00:04 am

Hi,

My opinion is to not run the main underground. Could the owner provide a soffit so you can run the pipe through the soffit with heat trace?

If not possible, I would recommend routing the underground portion of the main to not be under the building footprint or foundation.

Thanks,
Alex

Anthony

12/9/2021 07:41:38 am

From 13R 2016 ed:

6.5.2.1 Where necessary to place pipe that is under air pressure underground, the pipe shall be protected against corrosion.

6.7.2.3.4 Where steel pipe is used underground, the pipe shall be protected against corrosion.

There are provisions in 13 and 13R that are in place for running pipe underwound (see above). I would take a good long look at CH 10 of NFPA 13 (2016) which barrows heavily from NFPA 24 (all of it?)

Can you run fire protection piping underground, yes, however all the language in 13,13R and 24, I could find, is around mains leading to risers. I didn't find any explicit "you must have riser after pipe come up from underground." So not explicitly verboten? Maybe someone else here will correct me.

I think this is one of those instances where we as sprinkler people need to think a bit more like plumbers/site contractors. Water and pipe 100% can be underground. After all isn't that how all the water got into your building? Best practice I believe would have a control valve and thus a riser assembly on each side of the portion that is underground. If you're going a relatively short distance then it seems similar to running pipe through a crawl space. Make sure you're following all the rules for coatings and listings for UG pipe.

Best of luck.

Glenn Berger

12/9/2021 08:25:03 am

Whether or not it is explicitly permitted, your specific project may require it. I would recommend to do anything possible to avoid. But when necessary, proceed with caution.

Aaron Baumgartner

12/9/2021 08:54:51 am

Hello,

I once did a cellular data building with a common space at the street side of the building (bathrooms, owner offices, utilities), there were then 5 cellular tenant spaces which were essentially large data rooms, and an owner storage room at the far opposite end of the building.

The 5 cellular tenant spaces were protected with a dry agent systems, and also did not want any water traveling overhead to protect their equipment in the case of leaks. So to reach from the main riser located within the common space, to the opposite end of the building, we ran the main underground.

As Glenn said, I would avoid it if possible, but it can be done if necessary.

Regards

Danial Bartle

12/9/2021 09:00:00 am

I have not worked with 13R, but if the auxiliary drains requirements (more than 5 gallons) and the 5-year inspection requirements for MIC (NFPA 25)are similar to 13, I would imagine it would be costly and difficult to perform those properly and may be they way to prevent the underground installation.

Pete H

12/9/2021 09:39:26 am

Similar to the rest, I don't see anywhere where it's specifically forbidden. Follow Chapter 10 of NFPA 13 and NFPA 24 for all rules about underground pipe. I'd still call your local AHJ and give them the heads up that you're kind of tied to that unusual installation to smooth things over in advance.

Jesse

12/9/2021 09:46:19 am

There are a lot of reasons NOT to run sprinkler pipe (downstream of the check valve) underground. To protect it from corrosion, you'll probably need to use typical UG pipe so ensure that the appropriate C-factor is used in calcs. You also have the obvious inspection issues.

A much more favorable alternative is to run it in heated chase.

Joe

12/9/2021 10:22:38 am

I am very familiar with your situation. We have installed NFPA-13R systems in many multi-family residential buildings that have these open exterior breezeways which separates the buildings into many smaller buildings but covered by the same roof. Piping overhead is not an easy option. Due to the building code and fire rated separations the builder must maintain, they cannot create a heated chase across the breezeways, either on lower floors or attic without creating a fire rated enclosure, and in doing so would prevent heat from the soffit area you are trying to condition or protect.

Going underground is the option we have found safest to protect the piping from freezing. We call them underground loops which occurs at every breezeway. We use CPVC piping overhead and for the underground loops. CPVC is approved for underground piping. Each loop will need to be hydrostatically tested before cover and flushed for debris before connecting to adjacent side of building. We also install the piping a minimum 36” bury and sleeve the piping across the breezeway and under the building footings for added protection of the system main.

Heat tracing is another option but very expensive if installed with the full monitored control panel that should be installed.

sean

12/9/2021 10:53:01 am

Permitted but everything about it is more complicated.

Jack G

12/9/2021 01:16:44 pm

Cgapter 8 , 13, allows interconnection of breezeways from one service. Chapter 10 has a bunch of qualifiers, one if which is running more than 10 ft within a building. It is , underground, the best way to do this. 13 describes an accessable trench. What i ve gotton approved in the past is the underground slab portion of the trench is poured last, so the location is identified easily. I use rods to mark the joints( can be found with a parking lot magnant). In case of separation.
If running ductile, i use " tiger teeth" gaskets.

Nick P

12/16/2021 11:27:48 am

The previous post from Joe is what we typically see as well.
I have had very similar scenarios and just discussed this with the AHJ to confirm it was acceptable. They allowed the underground loop to cross the breezeways, but wanted an OS&Y valve installed when it entered each building. Also, they wanted us to use Blazemaster (or CPVC) piping for portion that was routed below grade.

Sprinkler Pipe Run Underground After Riser?

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