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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Clayton B Tibbetts
12/20/2022 08:06:11 am
Reference your local/state plumbing code.
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.
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.
12/20/2022 08:12:43 am
In Ontario the OBC under Table 22.214.171.124. 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.
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.
12/20/2022 11:30:30 am
12/22/2022 08:40:12 am
OK I cheated, yes I use cement-lined ductile iron piping.
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.
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.
12/20/2022 09:07:11 am
It is potable water up to the backflow preventer.
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.
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).
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.
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.
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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