What Mandates Ductile Iron Until the Backflow?

12/20/2022

We are doing the install for a new building. The fire sprinkler underground comes in the building and they are requiring ductile pipe be used inside the building up to the backflow preventer.

Can anyone cite literature for this?

I know NFPA does not require the use of back-flow prevention, but am interested in the code basis for the pipe type until the backflow preventer.

Thanks in advance.

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18 Comments

Clayton B Tibbetts

12/20/2022 08:06:11 am

Reference your local/state plumbing code.

Glenn Warga

12/20/2022 08:06:16 am

It is generally good practice to install Ductile Iron under building foundations. The local municipality is the entity that can specify installation methods and materials and the rules differ across the country. Many west coast jurisdictions require one piece stainless steel spigots under the foundation and into the building.

Anthony

12/20/2022 08:08:06 am

It may not be a code requirement, but a judgment call by the engineer/designer. They might think that the ground may not be suitable for PVC/CPVC or have seen too many installations that have neglected to properly sleeve pipe through foundations. There may be soil conditions that make DI the best call.

On the code front I have seen some jurisdictions require it on city drawings that look like they date back from the year one. It could just be that simple.

Corey Eppinghaus

12/20/2022 08:12:43 am

In Ontario the OBC under Table 7.2.11.2. of Part 7 gives you the list of acceptable piping material for a water service or FSM but it's really up to the engineer or designer of the UG and how that joint will be connected

12/20/2022 08:18:30 am

I am usually limited by the Design Specifications of the municipality I am working in. Usually there is a section for Watermain Pipe Material or something similar. They will typically reference the latest Standard of the American Waterworks Association (AWWA). Typically I will see the use of Brue Brute PVC piping stubbed into the building, and then Ductile Iron fittings and a uniflange for connecting to the backflow. Generally speaking, anything downstream of the backflow when connecting to a municipal water supply should be considered safe for potable water, which the AWWA standards enforce.

If you are trying to avoid a long run of ductile iron pipe within the building, I would connect the backflow to the water service as close as possible to where it comes into the building, and you can use your NFPA approved piping of choice upstream.

There may be NFPA codes that dictate the use of certain underground materials, but I have never had to dig that far since the AWWA standards will trump anything within NFPA anyways.

Glenn Berger

12/20/2022 08:19:45 am

I have not heard of a requirement that you need to use ductile to the backflow preventor.. Typically it is ductile iron underground and then carbon steel aboveground and then to the backflow preventor.

Eric R

12/20/2022 11:30:30 am

Glenn,

This approach is certainly incredibly prevalent, but I'd be concerned if this is something you are still doing today. We switched over to either concrete lined directly up to the backflow, or in situations where we can't make that work we will use victaulic grooved(not firelock) glavanized fittings that come with the NSF61 approval and A53 galvanized pipe. This should keep you in conformance with the IPC regs for water service piping per 605.3 and 605.5. A lot of water purveyors don't pay attention to sprinkler connections at this time, but sooner or later this will catch up with everybody so better to get ahead of it if you can.

The cost change can be negligible once you get your SOP set. One product we are really enjoying use of lately is a cement lined ductile iron MJ x Flanged elbow to slap on the bald stub-in pipe. Having the MJ connection allows you to align the elbow parallel with the wall (as opposed to spool flanges that are always wrong) and then flange connect directly to the backflow. All NSF, all UL listed.

Glenn Berger

12/22/2022 08:40:12 am

OK I cheated, yes I use cement-lined ductile iron piping.

James Phifer

12/20/2022 08:30:14 am

Per the appendix of NFPA 13, you should consider the weight that nonmetallic pipe would be supporting. i personally would not feel comfortable supporting a heavy riser with a backflow preventer with PVC pipe for example.

A.10.1.4.1 Where nonmetallic underground piping is provided
above grade or inside a building, the following should
be considered:
(1) Exposure from direct rays of sunlight
(2) Compatibility with chemicals such as floor coatings and
termiticides/insecticides
(3) Support of piping and appurtenances attached thereto
(e.g., sprinkler risers, backflow preventers) [24:
A.10.1.4.1]

Todd E Wyatt

12/20/2022 08:36:43 am

2021 International Plumbing Code (IPC) references “ductile” (8) times in Chapter 6 Water Supply Distribution but none of the references are a requirement of use. Table 605.3 Water Service Pipe lists (18) acceptable materials, “ductile iron water pipe” as being one. Table 605.4 Water Distribution Pipe lists (14) acceptable materials, “ductile iron pipe” as being one. Table 605.5 Pipe Fittings lists (17) acceptable materials, “gray iron and ductile iron” as being one. Lastly, Table 605.7 Valves lists (6) acceptable materials, “ductile iron water pipe” as being one.

2022 NFPA 13 references “ductile” (21) times but none of the references are a requirement of use.

When an AHJ lists a “requirement” such as this, it is perfectly acceptable to request from the AHJ the applicable Code reference. Sometimes, the AHJ cannot give the reference and will revise their “requirement” language to “recommended.”

David Kendrick

12/20/2022 09:07:11 am

It is potable water up to the backflow preventer.

chad

12/20/2022 09:28:26 am

Typically, prior to the backflow is covered by a standard or code that is not referenced by the I-codes or NFPA, like a local water department regulations, that are enforceable through some state or local law. Although 13 may come into play in parallel, the other local or state code will win, no matter how much you want to argue with the water department.

DAVE

12/20/2022 11:12:10 am

In my area the water purveyors and fire departments also accept stainelss steel, so I see a lot of Ames In-Building Risers, especially in retrofit situations. Continuing to the backflow preventer, I often see stainless GxG spool pieces and grooved stainless 90's. But I have had one or two AHJ's not allow stainless. Historically, we never allow galvanized steel in our specs, however a few GxG galvanized fittings are now certified ANSI/NSF61 for potable water, e.g., some Victaulic grooved reducers and standard-radius 90's (see their 02.06 Potable Water Approvals).

Ryan Hinson

12/20/2022 11:21:39 am

Piping upstream of the backflow is potable and must be appropriate for contact with potable water. This is typically found in the adopted plumbing code. Where adopted, IPC (2015 referenced here) Section 605.3 includes minimum allowable "water service piping" which must conform to NSF 61 in compliance with Section 605.3 and Section 605.4 which is for "water distribution piping" in the context of potable water.

Table 605.3 includes allowable pipe types for potable piping systems. Both DI and Galv CS are allowed for this application along with SS, plastics, brass, and copper. Though I think this is a bad idea for obvious reasons; in lieu of their listings, plastics listed in Table 605.3 but NOT in Table 605.4 CAN stub up through the slab up to 2 ft inside a building per NFPA 13 (2022) Section 6.1.4 and NFPA 24 (2019) Section 10.1.4.

Section 605.3 also states the following for "water service piping" which is typically buried:
"Ductile Iron water service piping shall be cement mortar lined in accordance with AWWA C104."

This should not be confused with "water distribution piping", typically above grade, which has no cement mortar lining requirement per Section 605.4.

Casey Milhorn

12/21/2022 09:59:51 am

I think this got covered in several comments, but it's more about the fact that it's cement lined DI pipe. This will be enforced by your water purveyor. Some accept PVC (like C900) and others strictly want Cl. 350, 50, 51, or 52 cement lined pipe and fittings. Where I am, we actually have to install mechanical joint DI fittings above ground when we have more than 1 cement lined flanged fitting to get to the backflow. It makes for some ridiculous looking installs and tons of weight hanging in the building. They don't like cement lined flanged fittings probably because they can't verify it's cement lined after it's installed.

sean

12/31/2022 08:52:24 pm

NFPA 13 and NFPA 24 have a variety of materials that can be used more than just ductile

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What Mandates Ductile Iron Until the Backflow?

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