Does an In-Building Riser Require a Thrust Block?

4/29/2022

Does an In-Building Riser require a thrust block?

I commonly see either mechanically-restrained pipe and fittings, or, an In-Building Riser (IBR) used when a fire service stubs into a building.

Is a thrust block required for the IBR?

https://www.watts.com/products/plumbing-flow-control-solutions/risers/ibr2

I can't seem to find any verbiage on the product data for Ames' IBR one way or another. Thanks for clarifying my confusion here.

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9 Comments

Alex

4/29/2022 07:24:36 am

Hi,

NFPA 24 (2013) Section 10.8.1.2 states that fused or "welded
joints shall not require additional restraining, provided that such joints can pass the hydrostatic test of 10.10.2.2 without shifting of piping or leakage in excess of permitted amounts"

From the installation guide provided, it appears that the only time additional constraints will be required is when you are testing just the riser or riser/main connection (Page 3)

Thanks,
Alex

Ryan Hinson

4/29/2022 09:00:42 am

The IBR itself, is considered restrained since it meets the criteria set forth in NFPA 24 (2013) Section 10.8.1.1 which requires compliance with EITHER Section 10.8.2 - thrust blocks, OR 10.8.3 - restrained joint systems.

The IBR is provided with a push-on inlet bell which includes welded tabs for rodding across this unrestrained joint in and of itself. Only then is this joint considered restrained per Sections 10.8.3(5) and 10.8.3.1. The upper end prep is either grooved or flanged which are both considered restrained per Sections 10.8.1.2 and 10.8.3(3) respectively. Therefore, additional restraint for the connections to THIS fitting are not required per Section 10.8.1.2.

The issue is whether the UG piping upstream of the IBR is restrained or not. Theoretically, just one unrestrained joint in a straight run of pipe can result in separation under sufficient internal pipe pressure. Therefore, each straight run of UG pipe should be 'bookended' with thrust blocking to prevent separation at any joint in between if every joint in between is not KNOWN to be restrained in accordance with NFPA 24 Section 10.8.

The owner may have additional requirements above and beyond the minimum set forth in NFPA 24 and cognizance of those requirements are recommended.

What you do or don't do could have a detrimental effect on portions of the UG piping system that are not in your scope.

Glenn Berger

4/29/2022 08:13:03 am

I would provide the thrust block. Typical a non-restrained joint will be placed at the 5 foot connection point to the exterior water supply and just a flanged or groove connection just above the building floor. I do not consider either of these as being truly a restrained or fused joint.

Eric

4/29/2022 09:36:56 am

By the code and spec sheet, Alex has the answer already. However from a real-world standpoint I feel it would depend on if you are installing just the IBR and another contractor would be connecting to it and installing the remainder of the underground piping, or if you have ownership of the entire underground scope of work. If you only have partial ownership I'd put in a thrust block as insurance, since you have no control over what happens to the other side of the connection.

The underground assembly requirements should be specified as either fully restrained, or requiring thrust-blocking at the bid document specification level. The allowable types of materials and fittings that can be used in each specific arrangement should then be specified. If you are the contractor and that isn't spelled out then I'd send an RFI, and if you're the designer/engineer then you need to decide which approach you are using first and then decide which products fit that approach.

As a sprinkler contractor I always push back on project specifications that call for the sprinkler fitter to install 5' out of the building and have the civil contractor install the remainder of the underground piping. This division creates so many headaches from a documentation and commissioning standpoint, and there is no valid reason why the civil contractor can't install the last bit of pipe inside the building up to the aboveground flange. They are frequently also the foundation contractor so it's not like they aren't already involved with the project. If there are licensing or qualification issues with this, then frankly they probably shouldn't be installing any portion of the fire service line, or should be doing that scope under sub-contract to the qualified fire contractor.

Splitting the scope creates problems with pressure testing, flushing, chlorination, restraint, and most importantly who is responsible for filling out and submitting the NFPA 24 completion certificate! It's well past time for this traditional spec book language to be updated.

Sorry for the rant. This topic is a sore spot for me!

Wes

4/29/2022 09:39:01 am

Eric - really appreciate your input here. Alongside Glenn Ryan & Alex's input I've already learned a lot this morning!

Ken Thackery

4/29/2022 10:34:50 am

NO! We have put 100's of these in the ground over the last 30 years, none have come out of the ground. Don't try to overcode this because of lack of experience, don't worry about the rest of the UG line if you're not contracted to install it. Rod the IBR to the UG pipe. Not required by any code, stop trying to change it lol.

Wes

4/29/2022 10:36:40 am

Asking for knowledge Ken; not trying to change anything. : )

Jack G

4/29/2022 01:50:30 pm

The underground to the building riser must be fully restrained to prevent separation along the push on joints. Nfpa 13,24.
If you are unsure— say you didn’t install the underground, but were responsible for the last 5 feet, then install a thrust block.
Common sense must prevail, you don’t want a system failure.

Casey Milhorn

4/29/2022 03:16:15 pm

I agree with ALMOST everyone on this. If you are installing all of the fire line, then do what needs to be done to restrain it. Rod and/or thrust block. A little common sense goes a long way here. If you are only doing the 5' out, I would definitely rod AND thrust block. If the utility contractor fails to connect to your rods, then you still have the TB to at least keep your end from pushing out. Who knows how much abuse the run-in is going to see during concrete pour, site traffic, and the utility contractor when connecting. This applies to even the SS lead-ins in my book. Don't ever assume the utility contractor knows what they are doing.

Does an In-Building Riser Require a Thrust Block?

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