Equipment & machines
Pipe plugs and pipe stoppers for PE pipes: types, dimensions and backpressure
Temporarily seal a PE pipe from the inside using a plug or pipe stopper: discover the available types, how to determine the size based on diameter and SDR, and what you need to know about backpressure and safety.
When to use a pipe plug or pipe stopper
A pipe plug or pipe stopper seals a PE pipe from the inside to prevent water, dirt or debris from entering, or to allow a section to be emptied and worked on. It is typically used during repairs and re-routing on existing pipelines, when draining a section prior to welding, during temporary separation of two systems, and as a barrier during work in a manhole or chamber.
The difference compared to squeeze-off is that the pipe is not deformed: the plug sits inside the pipe and can be removed again without the pipe wall having been compressed. This makes the method suitable for pressure lines where squeeze-off would permanently weaken the pipe.
A plug is work equipment, not a permanent barrier, and it does not replace a valve. If a pipeline must remain shut off during operation, an approved valve or equivalent permanent solution must be installed.
Types: mechanical plug, pipe stopper and bypass plug
Mechanical plug with expanding seal: the plug is inserted into the pipe and expanded against the pipe wall using a screw, spindle or handle so that the rubber seal creates a tight barrier. It typically withstands the highest backpressure and can remain in place for longer periods. Requires access to the pipe end and a tool that matches the diameter.
Pneumatic pipe stopper: a rubber bladder is inserted and inflated with a hand pump or compressor to the specified inflation pressure. It is quick to install, conforms to the shape of the pipe and is often used during repairs and draining, but withstands lower backpressure than a mechanical plug and its pressure must be monitored continuously.
Bypass plug: a plug fitted with a valve or nozzle allowing water to be drained or introduced while the pipe is sealed. Used during draining, venting and slow filling where sudden pressure surges must be avoided.
| Type | Installation method | Typical application | Note |
|---|---|---|---|
| Mechanical plug with expanding seal | Inserted and expanded against the pipe wall | Longer-term sealing, higher backpressure | Requires access to the pipe end and correct tooling |
| Pneumatic pipe stopper | Inflated to the specified inflation pressure | Quick sealing during repair and draining | Lower backpressure; monitor pressure continuously |
| Bypass plug with valve | Installed as a plug, valve opened as required | Draining, venting, controlled filling | Used to prevent pressure surges |
This table provides a general overview. Specific backpressure, inflation pressure and application ranges are specified in the manufacturer's data sheet for each individual plug or stopper – and the data sheet always takes precedence over this overview.
Dimensions: outside diameter, SDR and internal diameter
Pipes are specified by their outside diameter and SDR, e.g., Ø225 mm SDR17. The plug is sized according to the internal diameter, which is calculated from the wall thickness: e = outside diameter / SDR, and internal diameter = outside diameter - 2 x e.
For Ø225 mm SDR17, this yields e = 225 / 17 = approx. 13.2 mm and an internal diameter of approx. 199 mm. A pipe with the same outside diameter but a lower SDR (thicker wall) has a smaller internal diameter and therefore requires a smaller plug. This is the most common error leading to leakage: selecting the plug based solely on the outside diameter.
Always check the measured internal diameter using callipers or a ruler directly at the pipe end before selecting the plug. Pipes that have been squeezed, cut at an angle or feature internal weld beads may require a different plug type than indicated in the table.
| Outside diameter | SDR | Wall thickness (approx.) | Internal diameter (approx.) |
|---|---|---|---|
| Ø110 | SDR17 | 6,5 mm | 97 mm |
| Ø160 | SDR17 | 9,4 mm | 141 mm |
| Ø200 | SDR17 | 11,8 mm | 176 mm |
| Ø225 | SDR17 | 13,2 mm | 199 mm |
| Ø225 | SDR11 | 20,5 mm | 184 mm |
| Ø250 | SDR17 | 14,7 mm | 221 mm |
| Ø315 | SDR17 | 18,5 mm | 278 mm |
| Ø400 | SDR17 | 23,5 mm | 353 mm |
| Ø500 | SDR17 | 29,4 mm | 441 mm |
| Ø630 | SDR17 | 37,1 mm | 556 mm |
Wall thickness and internal diameter are calculated as approximate values (e = outside diameter / SDR, rounded to the nearest 0.1 mm) and may differ from the specific pipe manufacturer's dimensions and tolerances. Always measure the pipe before sizing the plug.
Maintenance and service life
Rubber ages. A pipe stopper that has been exposed to sunlight or chemicals can lose elasticity and crack precisely when it needs to hold pressure. Inspect seals and bladders for cracks, hardening and marks after every use, and replace them if in doubt.
Clean the plug after use and store it dry and protected from UV radiation. Follow the manufacturer's intervals for replacing seals, and check pressure gauges and pumps to ensure inflation pressure readings are accurate.