What Size Are Corporation Stops?

If you work with water service lines—even occasionally—you’ve probably heard someone say, “We just need a corporation stop,” as if it’s one universal part. In reality, corporation stops come in multiple sizes and connection styles, and the “right size” depends on more than a single number. One project might specify 3/4", another might call for 1", and yet another might mention CTS O.D. compression, copper flare, or AWWA taper thread—all while still using the same general name: corporation stop.

From our perspective at Ninghai Raising Copper Industry Co., Ltd., the most common sizing confusion happens because people mix up three different “sizes” that can all apply to one corporation stop:

• Inlet size (the side that threads/taps into the main or saddle)

• Outlet size (the side that connects to the service line)

• Service size / tubing O.D. (what the outlet must match, often CTS O.D.)

So, what size are corporation stops? The short answer: the most common inlet sizes are 1/2", 3/4", and 1" in many AWWA-style waterworks applications, but larger sizes exist depending on system design and standards.
The useful answer: you should size the corporation stop by matching (a) the main tap/inlet spec and (b) the service line outlet connection—not by guessing one number.

In this guide, we’ll break down corporation stop sizes in a way that’s easy to apply in procurement and installation: common size ranges, inlet vs outlet sizing, typical connection formats, and a practical checklist that prevents ordering mistakes.

1 What a Corporation Stop Is (Quick Definition)

A corporation stop is typically the first control valve off the water main for a service line, allowing installation and control of the service connection without shutting down the main.
Because it sits at the start of the service connection, it must match both the main tapping requirement and the service line connection requirement.

2 The Key Concept: Corporation Stop “Size” Is Not One Number

When someone asks, “What size are corporation stops?” they may mean one of these:

• Inlet size (e.g., 1/2", 3/4", 1")

• Outlet size (often sized to tubing O.D., flare thread, MIP/FIP, or compression format)

• Overall service size (the service line size the fitting is intended for)

• That’s why you’ll often see product naming that looks like:
  3/4" AWWA x 1" compression or 1/2" AWWA x 5/8" CB, where one side is the inlet and the other side is the outlet.

3 Common Inlet Sizes for Corporation Stops

In many waterworks systems, corporation stops follow AWWA-style sizing. Common inlet sizes frequently include 1/2", 3/4", and 1", with larger sizes also used depending on design.

Here’s what you’ll commonly see in catalogs and specifications:

Typical inlet size range (by common catalog offerings)

A broad range of inlet sizes may be available, including 1/2, 5/8, 3/4, 1, 1-1/4, 1-1/2, and 2 inches (availability depends on design type and system standards).

Pressure rating and size notes (AWWA style example)

Some AWWA plug-style corporation stops are specified for operating pressure (e.g., 100 psi on smaller sizes and different ratings for larger sizes), which also illustrates that “size families” matter in standards-based projects.

• Practical takeaway:
  If your drawing/spec says AWWA taper thread and an inlet size (like 3/4" or 1"), treat that as the primary “corporation stop size” for the main connection—then choose an outlet connection that matches the service tubing/pipe.

4 Outlet Sizes: Where Most Ordering Mistakes Happen

The outlet is where corporation stop sizing becomes “project-specific,” because service lines can be connected in several ways:

• CTS O.D. compression connections (very common in service tubing)

• Copper flare thread outlets (common for copper service connections)

• MIP / FIP outlets (threaded pipe connections)

What does “CTS O.D.” mean in sizing?

Many waterworks service fittings reference CTS O.D. (Copper Tube Size outside diameter) because the compression connection is designed around the tube’s outside diameter rather than a pipe’s nominal size. You’ll see catalog language like “compression connection for CTS O.D. tubing.”

Why it matters:
Two products might both be called “3/4-inch corporation stop,” but one has an outlet meant for 3/4 CTS O.D. tubing, while another uses a flare or threaded outlet. Those are not interchangeable without adapters—and adapters can add leak points and installation time.

5 A Simple Size Map: Inlet × Outlet (How to Read It)

When reviewing a corporation stop spec, read it like this:

Example format

[Inlet size + inlet standard] × [Outlet connection + outlet size]

Here’s a practical table that shows how to interpret the common ways corporation stops are presented:

(Manufacturers label slightly differently, but the logic is the same: inlet spec + outlet spec.)

6 What Sizes Are Most Common in Real Projects?

While project specs vary by region and utility standards, the most frequently encountered sizes in many water service applications tend to center around:

• Inlet sizes: 1/2", 3/4", 1"

• Outlet connections: CTS O.D. compression, copper flare, or threaded (MIP/FIP) depending on the service line design

Larger corporation stop families also exist (such as ball-type designs offered in larger sizes in some catalogs), often selected for higher flow service lines or specialized installations.

7 How to Choose the Correct Corporation Stop Size (Buyer Checklist)

When we help buyers avoid sizing errors, we recommend confirming these five points before ordering:

• Main connection requirement

Is the inlet AWWA taper thread? saddle? tapping spec? (confirm the standard and nominal inlet size)

• Service line material + sizing convention

Are you connecting to copper tube (CTS O.D.), PE service line, or threaded pipe?

Do you need compression for CTS O.D. tubing?

• Outlet connection type

Compression vs flare vs MIP/FIP

Confirm outlet size matches your service line specification (not just “about 3/4”)

• Operating pressure and application constraints

Some designs specify pressure limits by size and type; confirm project requirement aligns.

• Installation workflow

Which tapping/drilling machine or adapter is used? Some catalogs include adapter guidance by size/configuration.

8 Quick Reference Table: “What Size Corporation Stop Do I Need?”

Use this table as a practical starting point for discussion with your installer or engineer:

This keeps your ordering conversation structured: inlet first, outlet second, verify standards throughout.

Final Thoughts

So, what size are corporation stops? In waterworks practice, corporation stops are commonly available in inlet sizes such as 1/2", 3/4", and 1", with additional larger sizes depending on design families and utility standards. But the most important point is that corporation stop “size” is really two specs: the inlet size/standard for the main, and the outlet connection type/size for the service line—often referencing CTS O.D. compression, flare, or threaded connections.

At Ninghai Raising Copper Industry Co., Ltd., we work with buyers who need dependable service brass components and clear sizing support—from matching inlet standards to selecting the right outlet for the service line. If you’re preparing a project list or confirming corporation stop sizes for procurement, you’re welcome to learn more and contact Ninghai Raising Copper Industry Co., Ltd. for product information and selection guidance.

FAQ

1) What are the most common corporation stop sizes?

Many projects commonly use 1/2", 3/4", and 1" inlet sizes, but availability depends on standards and design families.

2) Why do corporation stops show two sizes in the description?

Because one is the inlet size (main connection) and the other is the outlet size/connection for the service line (compression, flare, or thread).

3) What does CTS O.D. mean on a corporation stop outlet?

It indicates the outlet compression connection is designed for Copper Tube Size outside diameter tubing, which must match the service tube O.D. spec.

4) Can I use adapters if the outlet doesn’t match my service line?

Adapters can work, but they may add leak points and installation complexity. It’s usually better to select a corporation stop with the correct outlet connection from the start.