Are Plumbing Pipes Reverse Threaded?

In the United States, water pipes and supply lines usually have a conical thread on the right.

However, some plumbing fixtures feature reverse threads to prevent the accidental connection of incorrect lines.

Copper plumbing pipes

This can be confusing for those who are not familiar with plumbing terminology, but it's important to know the difference to avoid costly mistakes.

In this article, we'll delve into reverse threading in plumbing pipes, equipping you with essential insights for informed plumbing project decisions.

Are Plumbing Pipes Reverse Threaded?

Plumbing pipes primarily feature standard right-hand threading, but reverse threading serves crucial purposes in certain scenarios.

Reverse threads are strategically employed to prevent erroneous connections that could result in significant issues.

This safety measure, borrowed from specialized applications like handling gases such as oxygen and acetylene, has a significant role in plumbing.

Reverse threads act as a safeguard, effectively preventing installation mistakes that could lead to leaks, floods, or other plumbing disasters.

Understanding the Structure of a Threaded Pipe Connection

The threaded pipes used in plumbing installations differ slightly from those used in bolts and lead screws.

They have a tapered thread that is slightly conical, which allows for a better seal.

If you're interested in the specifics of ensuring a tight seal, check out our related article on Rectorseal Vs Teflon Tape: Which Thread Sealant To Use?

The seal provided by a threaded pipe joint depends on multiple factors, including the labyrinth seal created by the threads and a positive seal between the two pipes.

The threads on a pipe are designed to fit together snugly so they don't leak when fluids or gases are flowing through them.

As mentioned, it's typical for water pipes and supply lines to have a conical thread on the right.

However, to avoid the accidental connection of incorrect lines, some plumbing fixtures are designed with reverse threads.

Why Are Plumbing Pipes Reverse Threaded?

Below are the specific applications of reverse-threaded plumbing pipes.

Prevent Lines From Being Mistakenly Connected

One of the main reasons plumbing pipes incorporate reverse threading is to avoid incorrect connections.

Using reverse threads is like a safety net that reduces installation errors and the risk of leaks while maintaining plumbing system integrity.

So, it's essentially a smart and safety-conscious move that helps keep plumbing systems in check.

Tighten the Connection

Another reason is to make it easier to tighten the connection. When you turn a pipe clockwise, the threads tighten and pull the two pipes together.

However, if you turn a pipe counterclockwise, the threads will loosen, and the pipes will separate.

Reverse threads make it easier to tighten the connection because you can turn the pipe counterclockwise, which will actually tighten the threads and pull the pipes together.

Avoid Cross Threading

Cross threading occurs when the threads on two pipes are not aligned properly, and they are forced together, causing the threads to strip or become damaged, which can lead to leaks.

Reverse threads help to prevent cross-threading by ensuring that the threads are correctly aligned before they are tightened.

So Plumbers Can Distinguish Between Pipes

Finally, plumbing pipes are often reverse-threaded so that plumbers can easily distinguish between different types of pipes.

For example, hot water pipes may be reverse threaded, while cold water pipes may not be.

This helps plumbers quickly identify which pipes they need to work on and ensures they use the correct tools and fittings.

Standard vs. Reverse Threaded Pipes

Standard threads and reverse threads are like right-handed and left-handed versions of screws or pipes.

We usually see the standard or right-hand threads because they're easier for right-handed people to use.

This is something that's been done for a long time since screws and pipes were all put in by hand.

Reverse or left-hand threads aren't as common, but they come in handy in special cases. They don’t get loose easily, which is good for safety and keeping things together.

Left-hand threads are also used to tell different pipes apart.

For example, gas pipes might have left-hand threads so people don't mix them up with water pipes. It’s a simple way to avoid mistakes and keep things safe.

Applications of Reverse Threading in Plumbing

Reverse threading is particularly useful in applications where vibrations or other forces may cause traditional threads to loosen over time.

Gas Pipes

Reverse threading is commonly used in gas pipes to ensure that the fittings are securely connected and that there is no risk of gas leaks.

Bathroom Fixtures

Another application of reverse threading is installing showerheads and other bathroom fixtures.

The reverse threads on these fixtures help to prevent them from becoming loose over time due to the constant flow of water.

Sprinkler System

Reverse threading is also commonly used in the installation of sprinkler systems.

The reverse threads on the sprinkler heads help to ensure that they remain securely attached to the piping system, even in high-pressure situations.

Are All Pipes Be Reverse Threaded?

Not all pipes can be reverse threaded. In fact, most pipes are not reverse-threaded. The threads on a pipe are determined by the application and the type of pipe being used.

Again, plumbing pipes are typically threaded with a conical thread on the right.

However, some plumbing fixtures do utilize reverse threads to avoid the accidental connection of incorrect lines.

As mentioned, gas pipe threads, for instance, are reversed. The male end of the connection is always tapered from the inside, and the female ends taper from the outside.

Final Thoughts

Understanding reverse threading in plumbing pipes is crucial for both professional plumbers and DIY enthusiasts.

As explored, reverse threading is a significant technique in plumbing, aiding in ensuring that pipes and fittings remain securely connected over time.

Regardless of the task at hand—be it installing a gas line, a showerhead, or a sprinkler system—utilizing reverse threading is beneficial.

It can contribute to maintaining a leak-free and properly functioning plumbing system over the years.

For those looking to explore connections without threads, check out our guide o on How To Connect Galvanized Pipe Without Threads?

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Many thanks to OpenAI's ChatGPT for helping fine-tune the creation of this article.