If you are looking for more details, kindly visit .
Grooved pipe systems make installing pipes in fire sprinkler systems and other applications easier and faster. The grooves allow quick, sure placement of couplings that create a water-tight seal without flanging or welding. Installers often need to join larger-diameter pipe to smaller-diameter pipe, of course, and there are several options to do it: reducing couplings, concentric reducers, and eccentric reducers. But which grooved pipe fitting is better suited for a specific job?
As with many things in fire protection, the answer is “it depends.” Here’s an explanation of when and why you might use each type of reduction (or expansion) device.
QRFS carries the equipment needed for your next project: check out our full selection of grooved fittings, including flexible and rigid couplings and adapters and reducers.
These two devices for connecting different-sized pipes share a characteristic: both reducing couplings and concentric reducers (sometimes called “conical reducers”) maintain the center axis of the pipes they join and the water flowing through them.
From there, they are a bit different: reducing couplings attach two different-sized pipes with less real estate in between them — the housing is 1.8”–2.4” wide, and the two pipe ends nearly touch —and only one coupling is required. In contrast, concentric reducers are “in-line reducers” that have a longer (2.5”–6”) funnel-like body that must be joined to the pipes on both sides by two standard, non-reducing couplings of appropriate sizes. So, using one part vs. three parts is a significant difference.
Both reducing couplings and concentric reducers enable transitions from a larger pipe to a smaller one (and vice versa). The main difference is that couplings are narrower, the transition is quicker, and fewer parts are involved. That said, concentric reducers may provide slightly better water flow than reducing couplings.
So, what about real-world use cases where one might be preferred over the other?
One possible consideration involves installing vertical pipe. To understand why, let’s review how installers join grooved pipes with couplings. They:
This video from Victaulic demonstrates a horizontal installation of a reducing coupling:
The potential issue in vertical installations is gravity. First, one must hold a long section of the upper, smaller pipe in place, maintaining the centerline while placing the metal housing around the gasket and tightening the nuts. And because the pipe sizes differ and gravity is what it is, there might be a risk that a smaller pipe will telescope down into a larger one.
Thus, some installers say they use concentric reducers because it’s a foolproof way to avoid telescoping. That’s because after they attach the concentric reducer — a small part that’s very easy to handle — to the lower pipe with a coupling, there is no risk of telescoping when attaching the upper pipe because the holes are the same size. Further, the top of the reducer presents a stable surface area that makes it easy to center the pipe while attaching and tightening the upper coupling.
But that said, high-quality reducing couplings either have optional steel washers or steel washers integrated into their gasket to prevent telescoping. For example, GemLock reducing couplings sized 2” and above have an integrated washer. So, when an installer places and aligns the upper pipe, the washer blocks that smaller pipe from sliding down into the larger one. And again, installers who use reducing couplings for vertical installations need fewer parts: one reducing coupling instead of two couplings and a concentric reducer.
Larry Greenberg, an engineer with Core & Main, which manufactures GemLock® grooved pipe systems, doesn’t believe there is always a 100% clear use case for using one over the other.
“A concentric reducer may give a little better flow, and we typically see that engineering companies tend to only go with them,” he says. “But other pipe fitters go with reducing couplings because they involve using fewer parts.”
The scenarios that call for using eccentric reducers instead of either a reducing coupling or a concentric reducer are more straightforward — and eccentric fittings are sometimes required. An eccentric reducer has a humped or angled shape that does not sustain the central axis of the pipe or water flow. Instead, the axis changes as these devices maintain the “BOP (bottom of pipe) elevation of the pipeline.”
Thus, the primary use case for an eccentric reducer is an installation scenario where “one of the outside surfaces of the pipeline is to be maintained the same” (top, bottom, or side). These reducers are typically used in horizontal pipe joining and suction pipe applications. Like a grooved concentric reducer, grooved eccentric reducers attach to the pipes they join with two standard grooved couplings of the appropriate sizes.
Despite the benefits of maintaining the bottom-of-pipe elevation, installing an eccentric reducer flat side down may cause issues in some applications where horizontal pipes carry liquids. Specifically, air can get trapped using this orientation. An exception is using an eccentric reducer that feeds a control valve: “flat side down will give a more constant flow through the control valve rather than a concentric reducer or eccentric reducer with flat side up, which will give you more flow disruption.”
There are few requirements in fire protection installation standards that govern which type of reducer to use. For example, NFPA 13: Standard for the Installation of Sprinkler Systems does not mention them under “groove joining methods.” It only references reducers in the section on welded fittings, and it’s not specific about their shape:
From the 2022 edition of NFPA 13
7.5.2.3.4 When the pipe size in a run of piping is reduced, a reducing fitting designed for that purpose shall be used in accordance with the requirements of 7.5.2.3.1.
Section 7.5.2.3.1 specifies the standards according to which various metal fittings must be listed.
But NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection has a requirement involving eccentric reducers. It mandates using them instead of concentric reducers to join the inlet of a suction pipe that connects the water supply to a fire pump:
From the 2022 edition of NFPA 20
4.16.6.4 Eccentric Tapered Reducer or Increaser.
Where the suction pipe and pump suction flange are not of the same size, they shall be connected with an eccentric tapered reducer or increaser installed in such a way as to avoid air pockets.
Commentary in the NFPA 20 Handbook (2016) specifies installing the eccentric reducer flat side up when “supplying the fire pump from below or the horizontal plane.” In contrast, “where supplied from above, the hydraulic institute recommends the flat portion of the reducer be installed on the bottom, with the actual reduction in pipe diameter taking place on the top of the fitting.”
Again, all these requirements — for using eccentric reducers on suction pipes and how to position them — aim to avoid trapped air, which is very bad news for fire pumps.
Picking a concentric vs. eccentric fitting also comes into play regarding drain caps, a different type of reducing fitting used for auxiliary drainage of a fire protection system. Eccentric drain caps, which have an off-center hole, should be used when draining water from horizontal pipes, whereas either concentric or eccentric drain caps work for draining vertical pipes. Read more about grooved fire sprinkler drain caps, including all their potential uses.
Aside from following the few NFPA rules, the ‘rules of thumb’ for using reducing couplings, concentric reducers, or eccentric reducers come down to:
When it comes time to tackle your next project, check out QRFS’s grooved pipe fittings, including couplings, caps, and adapters and reducers.
All these grooved fittings are UL Listed and FM Approved, conform to ASTM A536 Grade 65-45-12, and are made by GemLock, a New York-based manufacturer of quality grooved pipe systems.
Have questions or need help finding a part? Contact QRFS at 888-361-6662 or support@qrfs.com.
This blog was originally posted at QRFS.com/blog. If this article helped you, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.
Pipe reducers are one of the many types of fitting that can be used to control the flow within a piping system. In a piping system, there are two major types of reducer: concentric reducers and eccentric reducers. We’re going to talk about both types of reducer, what they are, and when you might use them. For the most part, reducing (and expanding) pipes is fairly straightforward. But there are some exceptions that are important to note for the health of a piping system.
First, let’s keep it simple: A pipe reducer is a pipe fitting that connects a larger pipe to a smaller pipe. Thus, it reduces the size of the pipe in the pipe system, from one size to another. Pipe reducers may frequently be used to connect pipes of different sizes. There are a variety of reasons why this might be done, and there are a variety of materials that could be flowing through the pipe, which is why there are different types of pipe reducer.
Like other pipe fittings, it can be very complicated to find the right pipe reducer. The fit can be complicated, and materials will matter. But once you find the right pipe reducer, the installation should be fairly simple and fast.
Reducers can be used simply to adapt pipes of other sizes, but there are also more complicated uses for them. They may need to be used when the flow has to be limited or expanded in a piping system, such as if the hydraulic nature of the piping system demands it. If you’re using a pipe reducer, you need to consider the consequences for the pipe system as a whole, because there will be changes in both flow and pressure.
Once you know that you need to use a pipe reducer, you need to make the decision between concentric and eccentric reducers. Most people are going to need to use a concentric pipe reducer, but there are some important reasons why an eccentric pipe reducer might be preferred.
While this may seem complicated, it’s actually quite simple. Concentric reducers reduce the pipe in the center. So, if you’re looking at the reducer head-on, you can see the smaller section is formed in the direct center of the larger side. Eccentric reducers reduce the pipe to the side. So, if you’re looking at the reducer head-on, you can see the smaller section is against one side of the larger side.
This may seem like a very simple change, but it does matter.
The cone-shaped concentric pipe reducer means the pipes have matched center lines, and the eccentric reducer has mis-matched center lines. Both of these have a consequence regarding flow. Most reducers are going to be concentric. Eccentric reducers are used when the pipes have to maintain the same top or bottom level. Eccentric reducers are frequently used to avoid trapping air within the system, so they are often used when both air and liquids may be flowing together.
Most people are going to need a cone-shaped concentric pipe reducer, because they aren’t going to need one side of the reducer to remain flat. But in many applications, either can be used, as long as the bottom of the eccentric reducer is placed correctly. The major concern about eccentric reducers is that they can collect liquids or gasses in one area if they are not properly aligned. When used vertically, there is essentially no difference between a concentric or eccentric pipe reducer.
It should be noted that while they are called reducers, reducers by their very nature are also expanders. They are simply used in the opposite direction as expanders. Thus, expanders can also be both concentric and eccentric, and the consequences of using one or the other to expand rather than reduce are the same. Either way, they are being used when a pipe of one size has to transition to a pipe of another size.
How a reducer is installed depends on the material that the reducer and the pipes are made from. If the reducer and pipes are made from metal, they can be butt-welded together. If the reducers are made of PVC, they will likely be fitted and glued. There are reducers that may have push-to-fit or crimp installations as well. It depends on how the reducer was made, the material, and the goals for the reducer.
To install the reducer, the reducer will be fitted on both pipes, and connected in the appropriate way. But care must be taken with eccentric reducers to ensure that the bottom of the eccentric reducer is properly lined up. In piping liquids horizontally, eccentric reducers need the flat side up, because otherwise gasses can collect. But in piping vapors horizontally, eccentric reducers need the flat side down, because they need to avoid collecting liquids.
The more the pipe is reduced, the more concerns there may be related to flow. If the pipe is only being reduced a little, then there shouldn’t be any complications.
Let’s say you already know that you need a concentric or eccentric pipe reducer. This isn’t the only thing you will need to know. Because you are connecting pipes, you will also need to know the material. There could be metal reducers, PVC reducers, PEX reducers, and so forth, each with their own method of connection. If you’re connecting two metal pipes, you might want a welded reducer. Otherwise, you might want one that can be fitted and glued.
You also need to know the sizes. Fitting for pipes can be tricky because they don’t go by the universal size of pipe. Instead, they go by the outside measurement for a male pipe, and an inside measurement for the female pipe. So, you need to know your type of pipe, and the exact size, and the exact material. One of the easiest ways to fit pipes is simply to bring the relevant pipes with you to match them up to the fittings.
When it comes to concentric vs eccentric reducer fittings, the initial choice of fitting should be obvious. That being said, finding pipe fittings is always complicated, and using the wrong pipe fitting can be disastrous. If you need to know more about pipe fittings, it’s time to consult with the experts. Check with Steel Forgings today to learn more about pipes and pipe fittings, and how to find the right concentric or eccentric reducers with rapid turnaround.
For more post tension system solutionsinformation, please contact us. We will provide professional answers.