You see “true union” and “double union” from different suppliers. This creates doubt. Are you ordering the right, fully serviceable valve that your customers expect every single time?

There is no difference. “True union” and “double union” are two names for the same design: a three-piece valve with two union nuts. This design lets you remove the central valve body completely without ever cutting the pipe.

I have this conversation often with my partner Budi in Indonesia. The terminology can be confusing because different regions or manufacturers might prefer one name over the other. But for a purchasing manager like him, consistency is key to avoid errors. Understanding that these terms mean the same superior valve simplifies the ordering process. It ensures his clients always get the serviceable, high-quality product they need for their projects.

What does true union mean?

You hear the term “true union” and it sounds technical or complicated. You might avoid it, thinking it’s a specialty item instead of the workhorse valve it actually is.

“True union” means the valve offers true serviceability. It has union connections on both ends, allowing the main body to be completely removed from the pipeline for repair or replacement without stressing the pipe.

The key word here is “true.” It signifies a complete and proper solution for maintenance. A true union valve is always a three-piece assembly: two connecting ends (called tailpieces) and the central valve body. The tailpieces are glued to the pipe. The central body, which holds the ball mechanism and seals, is held between them by two large nuts. When you unscrew these nuts, the body can be lifted straight out. This is different from a “single union” valve which only offers partial removal and can cause other problems. The “true” design is what we at Pntek build because it reflects our philosophy: create long-term, win-win collaborations by providing products that save our customers time and money over the entire life of the system. It’s the most professional and reliable design available.

What does double union mean?

You understand “true union,” but then you see a product listed as “double union.” You wonder if this is a newer, better version, or something else entirely, causing hesitation.

“Double union” is just a more descriptive name for the exact same thing as a true union valve. It simply means the valve has a union connection on two (or double) sides, making it fully removable.

This is the most common point of confusion, but the answer is very simple. Think of “double union” as the literal description and “true union” as the technical term for the benefit it provides. They are used to mean the same thing. It is like calling a car an “automobile” or a “vehicle.” Different words, same object. So, to be perfectly clear:

True Union = Double Union

Why do both names exist? It often comes down to regional habits or a manufacturer’s marketing choice. Some prefer “double union” because it physically describes the two nuts. Others, like us at Pntek, often use “true union” because it emphasizes the benefit of true serviceability. No matter which name you see, if the valve has a three-piece body with two large nuts on either side, you are looking at the same superior design. It’s what Budi needs to provide reliable solutions for his diverse clients in Indonesia.

What is the best type of ball valve?

You want to stock and sell the “best” ball valve. But offering the most expensive option for a simple job can lose a sale, while a cheap valve on a critical line can fail.

The “best” ball valve is the one that correctly matches the application’s needs. For serviceability and long-term value, a true union valve is best. For simple, low-cost applications, a compact valve is often sufficient.

“Best” really depends on the job’s priorities. The two most common PVC ball valves are the compact (one-piece) and the true union (three-piece). A purchasing expert like Budi needs to understand the trade-offs to guide his customers properly.

What is the difference between single union and double union ball valves?

You see a cheaper “single union” valve and think it’s a good compromise. But this can lead to major headaches for the installer during the first repair job.

A single union valve has one union nut, so only one side is removable. A double union has two nuts, making the entire valve body removable without bending or stressing the connected pipe.

The difference in serviceability is enormous, and it’s why professionals almost always choose the double union design. Let’s think about the actual repair process.

The Problem with Single Union

To remove a single union valve, you first unscrew the one nut. The other side of the valve is still permanently glued to the pipe. Now, you have to physically pull the pipes apart and bend them to get the valve body out. This puts huge stress on nearby joints and fittings. It can easily cause a new leak somewhere else in the system. It turns a simple repair into a risky operation. It’s a design that solves only half the problem.

The Advantage of Double Union

With a double union (true union) valve, the process is simple and safe. You unscrew both nuts. The central body, containing all the working parts, lifts straight up and out. There is zero stress on the pipes or fittings. You can replace the seals or the entire body in minutes, drop it back in, and tighten the nuts. This is the only professional solution for serviceable connections.

Conclusion

“True union” and “double union” describe the same superior valve design. For true serviceability and professional results, the double union connection is always the right and best choice.