What is a Bag Plug?

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  • Written By: B. Turner
  • Edited By: W. Everett
  • Last Modified Date: 11 November 2019
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A bag plug is a plumbing device used to quickly and easily seal off a plumbing pipe to stop leaks. These inflatable bags fit into a relatively small opening in or around the pipe, and can then be inflated to fill the pipe's entire diameter and stop the flow of liquid, gas, or debris. Bag plugs prevent plumbers from cutting into a pipe while making some types of repairs, and reduce time spent searching for leaks and other problem areas. Unlike many other types of plugs, a bag plug stops the flow almost instantly, which is particularly important during a plumbing emergency or gas leak scenario.

Each bag plug must be chosen based on the type of material contained within the pipe. Pipes containing gaseous materials or solid debris require a round bag plug design. These solid materials often include leaves or dirt particles that become trapped inside the plumbing system. The bag plug prevents these particles from proceeding through the system and causing damage to plumbing fixtures or other devices until the debris can be removed. Round bag plugs also block solid ingredients from contaminating finished products if a mistake is made during industrial production.


Because of the high pressure involved in most liquid plumbing applications, it's often more difficult to block the flow of liquid. Most liquid scenarios require a cylindrical bag plug instead of a round one. These cylindrical units extend further along the length of the pipe to better withstand pressure and reduce the risk of leaks.

Very large sewer or drain pipes require heavy-duty plugs that are sized to fit each pipe. Special bag plugs are also available for corrosive materials, high-pressure applications, and extreme temperatures. Manufacturers use materials like rubber or vinyl to produce these bags, though composite materials may be needed for better durability and strength in some applications.

Plumbers use a built-in pump to inflate the bag once it's been installed within the pipe. Basic units use rubber or metal tubing to connect a small hand pump to the bag. Very large units may require an air compressor or large-scale pump system.

In most situations, bag plugs only work when used on a temporary basis. They make an effective option for blocking the flow in a pipe during systems testing or repairs. These devices also help stop flow if water becomes contaminated due to biological or chemical spills, or any other cause. The bag plug prevents tainted water from reaching and sickening consumers before the problem can be remedied.


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