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Sch 7 pipe and other thinwall pipe

Sch 7 pipe and other thinwall pipe

Sch 7 pipe and other thinwall pipe

I am thinking of making a change to use more sch. 7 pipe, we do mannnnny jobs that have no or limited specs, many design builds and VE nearly everything.

I want to make the move to use more Dyna Flo type pipe or other thin-wall pipe. I have found that a stick of 4" x 21' dyna flow pipe is $6.00 cheaper, this means cheaper pipe and better sizes hydraulically.

I remember back in the days mid 90's - early 2000's we used a ton of Allied thin-wall pipe. Our supplies have said many companies in Georga & Florida used tons of this stuff.

Just trying to get some input. Perhaps from your experiences??

Thank you,

Eric Hendrix, SET
NICET Certified
Design Manager

RE: Sch 7 pipe and other thinwall pipe

Does Allied still make DynaFlow? For some reason I thought they were out of the sprinkler pipe market.

Up here on the Canadian prairies, lightwall always sold at a discount to import sch. 10, so that was all anyone ever installed. That changed a few years back, and now everyone uses import sch. 10 exclusively. I thought the price increase coincided with Allied's exit from the market, but I could be wrong.

RE: Sch 7 pipe and other thinwall pipe


From my research both of my fabricators can get sch 7 pipe and it is much cheaper.

Eric Hendrix, SET
NICET Certified
Design Manager

RE: Sch 7 pipe and other thinwall pipe

That's definitely the way I'd go, then. After googling it, I see that Bull Moose and Wheatland still make a lightwall pipe.

Anecdotally speaking, my last boss told me that they made the change from sch. 7 to sch. 10 before everyone else because his North Alabama welder kept warping the pipe from the heat.

RE: Sch 7 pipe and other thinwall pipe


Yes I have heard of this also, I could see where you might want an additional hanger here and there to help support the pipe from sagging


Eric Hendrix, SET
NICET Certified
Design Manager

RE: Sch 7 pipe and other thinwall pipe

I don't use sch. 7 primarily for the warping of the pipe when TOL's or GOL's are welded. Even at that if I'm using welded 1-1/4" pipe I'll use sch. 40 to avoid warping. Threaded sch. 7 is out of the question as I don't believe it is even made after the XL incident.

Mechanically it might be fine but looks sloppy when installed.

I imagine one could save some money on the fabrication but I stick to sch. 10 and 40. I've seen a few sch. 7 systems rot out after a short amount of time. Most sch. 10 has been treated to have a corrosion resistance ratio of 1 which is equivalent to sch. 40. For this secondary reason we don't use sch. 7.

RE: Sch 7 pipe and other thinwall pipe

I have customers that use Sch 07/30 exclusively, unless spec'd 10/40. Allied no longer makes, but you can get EddyFlow/Thread40 for your Sch 7/30 pipe.

I typically design with Sch 10/40. That allows the customer to go 07/30 if they prefer as the hydraulics are typically better. Now, there are some jobs where it can be worse, but those are rare and it is due to issues balancing areas.

Travis Mack
MFP Design, LLC
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: Sch 7 pipe and other thinwall pipe

I love when other contractors use Schedule 7, because, much like NewtonFP said, it rots out fairly quickly. We have replaced a TON of it in the past few years, and most of it wasn't that old. Personally, we only use schedule 10 & schedule 40. Saves having to worry about getting called back to chase leaks.

RE: Sch 7 pipe and other thinwall pipe

I have been watching with this conversation with a great deal of interest.

We use a lot of Schedule 7 and it's common for us to purchase 60,000 feet at of 2 1/2" at a time.

My favorite is Wheatland Tube specifically Mega Flow.

The Schedule 7 is either Wheatland or Bull Moose Eddyflow.

With the exception of 6" the UL CRR is equal to or better than sch. 40 pipe.

As a company policy we do not purchase any foreign pipe and for 6" we do purchase sch. 10 simply because of the CRR.

We have two certified welders in our shop and we do not use machines and we haven't had a problem with warping. When we used an automated machine to weld we did have warping problems but since everything is done individually by hand we haven't seen it. This said the smallest light wall pipe we use is 2" so that might be part of the answer as well.

Surprisingly our biggest experience with corrosion is with galvanized pipe.

RE: Sch 7 pipe and other thinwall pipe


I have had more issues with corrosion in galvanized pipe than regular black steel.

UNIFIED FACILITIES CRITERIA (UFC) for the Department of Defense https://www.wbdg.org/FFC/DOD/UFC/ufc_3_600_01_2016_c1.pdf now prohibits the use of galvanized pipe on all standard wet and dry pipe systems found on page 94 of the document:

Quote (UFC)

9-7.6 Piping.
9- Galvanized piping is only permitted for deluge sprinkler systems, valve trim piping and drain piping exposed to the Facility exterior.
9- Black steel pipe must be used for the addition, repair or relocation of existing galvanized pipe in wet pipe, dry pipe or preaction systems.

9- Black steel pipe with furnace butt-welds (ASTM A53, Type F) must be used.
9- Electric-resistance-welded steel pipe is not permitted.
9-7.6.2 Piping 2-in. (50 mm) and less must be minimum schedule 40. Piping larger than 2-in. (50 mm) must be minimum schedule 10.

Does anyone know FM Global's latest stance on dry systems and galvanized pipe?

RE: Sch 7 pipe and other thinwall pipe

Good stuff, I know in the boondocks of MS I have steered us away from galvanized piping especially after the language changed in NFPA 13 2016 edition either though the state is still using 2013 edition.

I am still very iffy about using Sch. 7 but I do think I am going try and steer us toward using it in wet systems on a trial basis. Some of the questions folks here brought up is will the fitter's know how to properly groove sch. 7 pipe?


Eric Hendrix, SET
NICET Certified
Design Manager

RE: Sch 7 pipe and other thinwall pipe

FM 3-0 Section 3.2 still allows a C Factor of 120 for Galvanized while only allowing 100 for black steel.
FM 2-0 Section also states where galvanized or stainless pipe must be used (black steel only allowed on dry pipe with inert gas btw).

FM have however done a very intensive technical report (in 2014) called "Corrosion and Corrosion Mitigation in Fire Protection Systems". The report is not favourable at all to galvanized pipe, however they have not updated their datasheet accordingly and any of the FM projects I've been on in recent times has still had galvanized pipe for dry type systems. However FM criteria is so project specific (from what I've seen - some extreme variations from their datasheet occur if their customer has a big enough stick), that I would specifically look into the pipe specs for every project.

RE: Sch 7 pipe and other thinwall pipe

There are definitely cost saving implications when using the Flow/Thread pipe instead of 10/40. I have a mixture of client preferences that I deal with. If there are no specs, they use the Eddyflow/Eddythread40. Corrosion is on everyone's mind nowadays, it seems. What I am starting to see more and more of, both in practice and in specifications, is allowing the Schedule 7 pipe for grooved situations, but restricting the pipe to Schedule 40 when threaded.

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