Is SDR21 OK for Combined Domestic/Sprinkler?

2/19/2024

We have a private water main feeding a combined domestic and NFPA 13 system that was specified as C900. They installed SDR21 (6") instead.

They are using the argument that this 200 psi rated pipe will not be subject to the fire system pressure and therefore is ok.

I cannot find where this is listed for fire service mains. Any direction?

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8 Comments

Glenn Berger

2/19/2024 08:11:44 am

Most municipal water systems have underground water mains that supply both domestic and fire use and do not use NRTL fire system approved piping.

I see no issue here, except contract non-compliance which apparently did not have proper oversight.

Anthony

2/19/2024 08:20:31 am

SDR -21 is covered by AWWA C605-21 I think. Thats not a recognized standard in NFPA 13 nor NFPA 24.

If you allow the substitution, then you're taking on the responsibility for any problems with a water main that's buried. I like to stay away from those kinds of problems personally. I'd make them re pipe it. Or paper yourself very heavily away from any liability.

Scott McBride

2/19/2024 08:24:33 am

If they specified C900 in the approved plan review, they must get the AHJs approval before installing an alternative. As for the piping itself so long as it meets the requirements of NFPA 24 there should be no issues. Depending on your fee schedule they could be cited for installing non-approved piping per the plan review without prior AHJ approval.

Scott McBride

2/19/2024 08:31:49 am

The approved piping is per NFPA 24 Table 10.1.1.1 and at first glance SDR-21 is not an acceptable alternative. Unless I am missing something.

Franck

2/19/2024 10:09:39 am

As indicated above, the final situation might be acceptable for its use, but it is more a liability issue and who will be responsible at the end if you accept it.
If it was specified as C900, they should have installed C900.
If a deviation was necessary (or more comfortable for the contractor) it should have been asked prior the installation.
The question is : would it be considered acceptable by AHJ if asked prior to installation ? If the answer is no, it is still not acceptable !

Casey Milhorn

2/19/2024 10:36:57 am

As others have said, put your concerns in writing, divorce yourself from the liability as much as possible, and move on. I assume you are the contractor and not the engineer of record.

From a practical stand point: Should be fine and I assume the FDC is on the downstream side of a double check valve assembly and won't be an issue if/when they energize the system. Unless city pressure consistently is known to have water surge in that area and reaches 175 psi and over, should be fine from that perspective.

From a code/standard point: The water department standards should rule here (before the individual backflows). If they are okay with DR21 for domestic use, should not be an issue for combined use either.

From a contract perspective: If you aren't the specifier, engineer of record, etc... and only the installing contractor, you should be fine. As others stated, voice your concern in writing that it deviates from the contract documents and move on. I assume you probably calculated with DR18 so your calcs should have a little extra cushion now that you have larger ID pipe.

By the way, this arrangement is not very common, at least in our area. Every water dept here either asks for a master meter at the road, and then they will allow a combine service line for full 13 systems, or they just don't allow this arrangement at all. It can have it's downsides, especially for the water dept.

Robert Morgan

2/19/2024 01:44:22 pm

Unfortunately our State (Illinois) health department now requires combined domestic and fire lines. We typically have a meter pit with an F-2 meter, the split occurs inside.

Mark Harris

2/19/2024 05:04:34 pm

FM approved C900 fire mains are DR14 for Class 200 and DR18 for Class 150 (think may change above 12"). I would be curious what the water company uses? If they use DR21 (which my bet is no) then like most comments above say will it work, yes. Is it correct if spec said C900 fire main, no. The lower the DR the thicker the pipe wall and higher cost per foot. If install is accepted the end user or general contractor could be justified asking for a credit. If they have to give money back maybe the site utility contractor (most likely) that installed the DR21 will read the spec next time. Hopefully they transitioned to ductile iron outside building and did not bring the plastic above through basement wall or above floor.

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Is SDR21 OK for Combined Domestic/Sprinkler?

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