How to Choose the Right Pipe Plug

Investing in the proper plugs for your job saves time and prevents costly leaks

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Pipe plugs play a crucial role in ensuring efficient and reliable plumbing systems. Selecting the right option is essential whether the pipe plugs are used for testing, isolation, or temporary closure.

An unsuitable pipe plug can result in leaks, bursts, system failures, and physical injuries. 

Several types of pipe plugs are available, each with unique features and functionalities. Two common types include blocking plugs and bypass plugs. Understanding the differences between the two will help determine the best fit for your job.

Blocking plugs

A blocking plug is commonly used during maintenance, repairs, or testing of pipes to block the flow of water or other fluids in a plumbing system. These plugs provide a watertight seal and prevent the flow of fluids through the pipe.

Blocking plugs are versatile and can effectively seal various types of pipes, including out-of-round ones that lack perfect roundness. Typically made of natural rubber, these plugs are known for their superior sealing properties and excellent expansion and memory capabilities.

Mechanical cleanout plugs are frequently used for pressure testing or temporary blocking of pipes. Made from high-quality rubber, these plugs have a mechanical mechanism allowing easy installation and removal. They are suitable for water supply and DWV (drain, waste and vent) systems and come in various sizes and pressure ratings to suit a range of plumbing applications.

Long test-ball plugs are a quick and secure way to halt the flow of water or other fluids during waste stack testing without complex valve systems. Made of natural rubber, these plugs deliver an excellent seal for both the rise and run during tests and have a ring-and-chain assembly to prevent them from being drawn into the DWV system during testing.

Bypass plugs

Bypass plugs are specifically designed to temporarily stop or redirect the flow of water or other fluids. They are typically used in situations where certain sections of the plumbing system need to be isolated or bypassed for maintenance, repairs, or testing purposes. Using these plugs makes it possible to test and monitor pipes up to 96 inches in diameter.

Plumbing muni-balls can be used to block flow or as back plugs for sewer air testing. They can fit multiple pipe diameters, effectively sealing both round and out-of-round pipes. They also feature a removable inflation valve for easy use. Made of durable natural rubber, it fills the roughest surfaces and can be converted to an air test plug using a conversion kit.

Choosing the correct pipe plug

Here are some guidelines to help in the selection process: 

Match the pipe size

First and foremost, ensure the plug is made for your pipe’s inside diameter. Pipe sizes are standardized, so match the plug’s stated size range to your pipe’s ID. Pipe plugs have a minimum and maximum sealing size range. An undersized plug won't seal, and an oversized one is a safety hazard. Ensure that the plug you choose is compatible with the pipe size you are working with.

While some plugs may be compatible with multiple pipe sizes, ensuring they are used only on pipes whose diameter falls within the specified range is essential. Refer to the pipe plug manufacturer’s detailed sizing charts to pick the appropriate size range or contact them for further assistance. 

Know the type of system

Different pipe plugs are designed for specific systems, such as DWV or water supply. Some plugs may have features tailored to the requirements of a particular system. For example, water supply plugs have higher pressure ratings and are designed to provide a secure seal for testing purposes. Ensure that the pipe plug you choose is specifically designed for the type of system you are working with to ensure optimal performance.

Understand the plug purpose

Pipe plugs can serve different purposes in plumbing, including testing systems, temporary blockage for repairs, or conducting sewer air tests. Each purpose may require different features or capabilities from a pipe plug. For example, if you run tests on a DWV system, you do not need a plug with a high-pressure rating. A lower-pressure rated plug will ensure a reliable seal. Evaluate the specific purpose you have in mind and select a pipe plug that is designed to meet those requirements.

Ease of use

Consider the ease of installing and removing the pipe plug. Some plugs may require additional tools for installation, while others can be easily installed or removed by hand. Assess your level of experience and the resources available to you.

Match the pressure rating

Pipe plugs are rated for maximum back pressure thresholds. Always choose a plug rated more than the system pressure you need to contain. Exceeding the pressure rating risks the plug blowing out, causing safety hazards and system damage. When in doubt, choose a higher-rated plug.

Whether you are using a plug for testing, maintenance, or repair, using the appropriate plug for your application is essential. At Cherne, there is a Plug Selector Tool that helps you find the correct plug for your job in a few easy steps.

Caring for and storing pipe plugs

Caring for and storing pipe plugs is essential to their long-term maintenance and efficient use. Store pipe plugs indoors in a cool and dry place. Avoid exposing them to direct sunlight or other ultraviolet light, which can damage the plugs. 

After using pipe plugs in dirty or rocky pipes, clean them thoroughly to ensure long-term function and avoid contamination. Proper care and maintenance of pipe plugs ensures their longevity and protects the plumbing system and surrounding environment from leaks and other damages. 

With proper selection, usage, and storage, pipe plugs can temporarily seal pipes safely and effectively. Refer to manufacturers like Cherne for more detailed information on sizing and applications.

About the Author

Sean Comerford is a technical applications manager at Oatey Co. He is a third-generation tradesman with nearly 20 years of plumbing experience. He can be reached at


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