We had the opportunity to consult with our wastewater technology specialist on the proper application of pipe plugs, shut-off discs and inflatable stoppers.
Pipe Plugs up to 8 Bar with Bypass – How Are They Used?
Question: I need to deal with a change in pipe diameter. How can I use your pipe plugs with bypass, which are rated up to 8 bar, without the plug slipping inside the pipe?
Answer: Simply insert the plug into the pipe. If a change in diameter is needed, turn the screw on the plug. Turning the screw compresses the two plates together, which in turn expands the rubber ring between them and creates a tight seal. For example, the DN 25 plug can be expanded up to 29 mm and used in pipes with an internal diameter of 27 mm. The DN 50 plug has a working range from 48 mm to 55 mm, and so on. This means that a single plug can cover a wider diameter range, offering flexibility in application.
Question: Your website states that plugs must be secured when facing counterpressure over 1 bar. Why is that necessary, and how is it done?
Answer: Pipes often contain oils or grease, which can cause the plug to slip. Most systems are pressure-tested with air, and with each additional bar of pressure, the volume of air doubles. Depending on the situation, the plug can be secured with something like a board braced in front of it. The method of securing depends heavily on the specific environment: securing in a manhole is different from securing inside a building. If people are working in front of the plug, securing is absolutely essential. Also, if the rubber is installed warm and later cools down, it can shrink and become loose. In industrial settings where no personnel are present during testing, securing may not always be required. There’s no universal rule for how to secure a pipe plug. In ceiling or wall installations, or in underground sewer applications, the approach can vary significantly. For metallic pipes, our expert recommends using a clamp to secure the plug. This wouldn’t work with plastic pipes, where a wooden brace pressed against the wall might be more appropriate.
Pipe Plug, Shut-Off Disc or Inflatable Stopper – Which One to Use?
Question: When should I use a pipe plug, a shut-off disc, or an inflatable stopper?
Answer: For decommissioning old, non-pressurised pipelines, shut-off discs are suitable. They can only withstand low pressure, and are used when a non-pressurised line needs to be taken out of service temporarily and later reactivated. For a more permanent solution, a pipe plug is the better choice – especially in water pipes, where operating pressure is a factor. Pipe plugs are designed to withstand such pressure levels. Inflatable stoppers are ideal when flexibility in diameter is needed. However, they are only rated for low pressure – up to a maximum of 1 bar. Their main advantage is that one stopper can cover several diameter ranges, which would otherwise require multiple discs or plugs. This makes them more cost-effective in some situations. However, they are not a long-term solution. Pipe plugs, on the other hand, can remain in place long term if they are inspected annually. That said, the rubber will degrade over time, so they are not a permanent solution in the absolute sense. Stainless steel plugs are rust-resistant and suitable for long-term use. One limitation of plugs is that they are less flexible when it comes to sudden changes in pipe diameter.Ultimately, the decision of which solution to use is often case-specific. Especially in industrial settings, there are many different application scenarios where one option may be more appropriate than another.
Flexible Pipe Stopper with Tyre Valve vs Standard Inflatable Stopper
Question: We stock Inflatable PVC Sealing Bags 30 - 320 mm the MOWOTAS shop. When should I use this type, and when is a standard inflatable stopper more suitable?
Answer: The blue inflatable stoppers (flexible PVC pipe stoppers with a tyre valve) can’t withstand as much back pressure as standard inflatable stoppers. They are mainly used for quick shut-off tasks, such as emergency situations in domestic settings. One of their key advantages is that they can be inflated easily using a standard bicycle pump, making them highly practical for private users. Additionally, the price of blue inflatable stoppers is lower than that of standard stoppers in the same size range. Standard inflatable stoppers, on the other hand, require inflation using a compressor, which can be off-putting for private customers. In terms of durability, standard inflatable stoppers are clearly superior to the simpler blue model. The blue stopper also requires more care and maintenance. It is suitable for lighter applications with low internal and back pressure, such as blocking water backing up from a basement toilet or shower. They have also been used on newly constructed flat roofs, where numerous low-pressure drainage points exist. The blue inflatable stopper can be quickly inserted, inflated, and then deflated again with minimal effort. It's a convenient solution for temporary and low-pressure sealing needs.
Do you have questions about our pipe sealing products for use in wastewater applications? Our experts will be happy to advise you.
Author: Dr. Daniela Brandt
You can find out more about the person who wrote this article on Linkedin.
