Can a 90-degree Elbow Be Beneath a Footing?

9/2/2024

Can a fitting (a 90-degree elbow) from a fire ductile iron water line be under the footing, which turns the pipe up into the Fire Pump room?

In other words, the pipe feed comes from a water tank underground, then turns up with a 90 under the building footing and the pipes through the footing.

Is this acceptable?

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7 Comments

Glenn Berger

9/2/2024 08:10:03 am

With coordination of the structural engineer / designer, it can be permissible. It would be best if a properly sized sleeve was engineered into the footing. A thrust block is still required below the elbow.

Joe

9/2/2024 08:20:38 am

Per code Yes, but code limits the distance from the exterior wall to the elbow to 10 ft. My understanding is that they want to limit the number of fittings under the building to just the elbow below the vertical riser.

NFPA-13(2019)
6.4.3 Private Fire Service Mains Under Buildings. Except as allowed by 6.4.3, private fire service mains shall not be allowed to run under buildings. [24:10.4.3]
6.4.3.1* Private fire service mains supplying fire protection systems within the building shall be permitted to extend no more than 10 ft (3.0 m), as measured from the outside of the building,
under the building to the riser location. [24:10.4.3.1]
The requirement in 6.4.3.1 permits a riser lead-in main to run underneath the building’s footing or to penetrate the foundation wall if the main rises through the floor slab within 10 ft (3 m) of the building’s exterior wall.

Dan Wilder

9/2/2024 11:48:39 am

Can you, yes. It will take a sleeve through the footing, an increase in the stem wall/footer design (to make up for the lesser sq in area) and a structural sign off. Getting someone actually sign off will be difficult...like this is the ONLY way.

Jack G

9/2/2024 01:56:29 pm

Yes you can but why would you.
I dont like joints under footings. A leak over years could wash away the soil under the footing causing it to collapse. Saw it happen while testing an old pump in wilmington delaware about 54 years ago. Under ground leaked under the foundation. Cast iron fire main. Church of the Home Foundation. What a bad thing to happen.
I always use tiger teeth retainers on my underground piping. ( mega lugs another name)
A horizontal fire pump requires 3 feet of head above the suction flange. Was the tank capacity sized for the " dead " water?
I would go under the floor so the joint is past the foundation . Have a sleeve ( galv metal schd 80 ) under the footing sized per code.
Go up thru the floor ( plastic sleeve) schd 40.
Tiger teeth retainers. Rodding not required)
Elbow back to wall turn into pump with another elbow. ( grooved firelock )

Jay

9/3/2024 08:58:12 am

No you cannnot. I assume this would place the joint of the elbow under the footing which is not permitted by NFPA 24.
See 2025ed NFPA 24:10.4.3.1.1 and Figure A.10.4.3.1

Ted S. link

9/4/2024 10:21:08 am

Normally the FP Engineer is supposed to have the Structural Engineer "drop the Footing" at that location. It is not expensive and done all the time with water lines. I was advised once by a Structural Engineer not to do it because then you have all of the loads on the footing now on the piping.

10/4/2024 09:57:00 am

Surprised no one mentioned an in-building riser ( Ames IBR) . No joints below slab pipe. Personally, I'd only sleeve a footer if no other possible option available

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Can a 90-degree Elbow Be Beneath a Footing?

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