Pros & Cons to Using Schedule 7 Pipe?

11/3/2021

Our project includes a warehouse ESFR fire sprinkler system.

We specified minimum Schedule 10 for all pipe. The contractor has proposed Schedule 7 for use in the 2-1/2" and 4" diameter pipe.

Any pros or cons to using Schedule 7 that you'd recommend from experience?

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

12 Comments

Sidney T Forin

11/3/2021 08:14:25 am

Check the levels of MIC in the local city water system, we've replaced a lot of schedule 7 pipe with pin holes in certain areas where the levels of MIC was high.

Anthony

11/3/2021 08:16:50 am

Its thinner, so obvious downsides from a life span and durability stand point.

The benefits come from cost obviously and also its flexibility. The pipe is slightly easier to bend so it can be easier to install under a rolling pitched roof where you're going to let the flexing in the pipe and couplings track the roof pitch rather than swing joints. It can be slightly easier to install which the fitters might appreciate or they might complain that its as wobbly as a pop can, good luck making 'em happy.

This is a common practice in warehouse applications and I wouldn't have a problem allowing it as a specifier/engineer as long as the cost savings were passed on to the owner. Appx 20%~30% reduction in pipe cost.

David Kendrick

11/3/2021 10:09:34 am

This caught my eye.

The 20% to 30% number must be from a market different than ours.

Schedule 10 to Schedule 7 price comparison rounds to 11%.

Since we're discussing thinwall pipe I didn't compare pricing to Schedule 40 or 80.

Also NFPA 13 restricts the schedule of pipe that may be bent. Schedule 10 steel pipe and heavier. Unless its listing includes bending.

Personally I've only installed Schedule 7 pipe as structure to support my chain link fence.

Anthony

11/16/2021 08:35:02 am

It was the number thrown around our office when ordering I was never the purchasing agent so I may be off on the cost savings.

I'm not talking about bending the pipe, I'm talking about the natural flex in the pipe. Bending involves 'plastic deformation' of the pipe. flex is the elastic bending in the pipe such as a spring would experience.

Over a 100' span its not unusual to see the pipe be able to take up a 1'-0 differential in roof elevation especially with the ¼~¾ deg of cheat you can get out of a grooved coupling

Dan Wilder

11/3/2021 08:17:01 am

Pros
-Lighter
-Better Hydraulics = Smaller pipe size (potentially)
-Cheaper

Cons
-Less wall thickness = potential for faster corrosion leaks to appear
-Tends to warp on larger welded outlets or multiple outlets on a line

Since warehouses tend to be an "install and leave as is", if you can get a majority of the air out to reduce the trapped air/water interface locations there shouldn't be an issue. If this is in an area with "harder" water (I'm in Phoenix, all of our water is considered "hard" due to the chemicals put in to keep it potable) I would stick with Sch 10 at a minimum.

Jesse

11/3/2021 08:22:37 am

I guess my answer would depend on why Schedule 10 was specified. We find a lot of institutional projects spec Sch. 40, but find that their general spec requirements are often times decades old. When we present them with reasons to use Schedule 10, they often see benefit.

In your case I'm curious as to whether Schedule 7 was suggested for cost reasons, or something else. Sch. 7 pipe has a larger inside diameter so it performs a little better hydraulically, but I'm not sure in your case that's why they want it. I'd be curious to know why. My bet would be on material cost.

Shawn Hoyer

11/3/2021 09:31:38 am

The main issue is corrosion at the peak where there is the water/air interface as Dan had mentioned. Even if the system is designed and installed to help alleviate the trapped air, there will be portions where the air will still be trapped and corrosion will happen. The question is how long before it happens.

I would take into consideration the needs of your client and what your relationship is to that client. There are many factors that affect how to best serve each individual. Most of them depend on you understanding their needs. Start with what their intent is with the building.

If they are a "short term" owner/developer and would be looking to sell off the building with maximum profits, then go ahead and allow the use of the Schedule 7 pipe assuming their is a cost savings. The issues with pipe corrosion would be the next person's problem.

However, if this is a "long term" investment that they intend to hold on to, I would definitely recommend Schedule 10 as a minimum and ensure that the system(s) are designed and installed to alleviate as much trapped air as possible. Neither of which should have a cost impact over what you had specified.

You know your client and what's important to them. Base your recommendations on that and make sure you keep the client informed on what they are buying. The last thing you want is to have a client that thought they bought the Cadillac and found out it was a Pinto.

Lucas Kirn

11/3/2021 10:00:43 am

I echo Shawn’s comment above. It’s important to consider the owner’s plan for the building - short term build and sell or long term hold? Another consideration is what the building is being used for. Is it basic storage of dry goods or is it a production facility or fulfillment center that would be more sensitive to business disruption if the sch 7 pipe begins to experience leaks/failures?

Dave

11/3/2021 10:37:24 am

Probably not a deciding factor, but don't forget that the lateral sway bracing section of NFPA #13 requires you to comply with the maximum load tables in NFPA #13, or if it is not one of those pipe types (e.g., S40, S10, S5), you must use the values published by the manufacturer. (Some brace calculations software prompts you of this requirement.) Wheatland and Bull Moose for example have pdf maximum load tables for their versions of flow-pipe.

Robert Allan Kluck

11/3/2021 02:01:07 pm

You don't mention the material (Carbon Steel or SS). If it is Carbon Steel, the risk of MIC might be high, especially if your city water that will fill the system is more chemically active( or if the area is a chemical or salt air environment). If it is stainless steel, then the risk of corrosion goes down substantially.

sean

11/5/2021 06:26:53 am

I see the most common reason in my area to use schedule 7 is weight. Easier on the field guys to move it around.

Alex

11/5/2021 07:15:21 am

Hi,

Long story short - if you specified schedule 10, go schedule 10. If you do allow the schedule 7, make sure you look for a credit.

In my opinion, I would say the minimum should be schedule 10. If you have hard water, you can be looking at pinholes within a few years. BUT, say you are adding a temp system (complete or even just egress) to be removed within a year, then corrosion and pinholes shouldn't be the deciding factor.

Thanks,
Alex

Pros & Cons to Using Schedule 7 Pipe?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES