How it connects
Insert the deflated rubber plug into the pipe, then inflate it so the body expands radially against the bore and forms a circumferential seal. Deflation releases the contact for removal.
Male and female halves
The inserted plug can be described informally as male; the receiving surface is the pipe bore. These are normally specified as a plug and compatible pipe diameter, rather than a standardized male/female connector pair.
Usually connects to
- Interior bore of a pipe within the plug manufacturer’s specified diameter range; Interior bore of a pipe within the plug’s rated diameter range
Common sizes
- Single- and multi-size inflatable plugs must match the actual pipe-ID range, not just deflated diameter.
- Cherne Single-Size Test-Ball versions include nominal 1-1/4–1-1/2, 2, 3 and 4 in; 270032 is nominal 3 in. Another application uses nominal 4 in.
Where it is used
Drain, waste and vent testingSanitary and storm sewer maintenanceTemporary pipe flow blockingDrain, waste and vent (DWV) plumbing tests
Variations
- Multi-size blocking plugs
- Long test-ball plugs
- Bypass inflatable plugs, with a separate flow-through passage
- Single-size inflatable test plugs
- Inflatable plugs with different rated pipe diameter ranges
How to recognise it
Look for an inflatable rubber body, often with circumferential ribs, and an inflation valve or hose. The outer body goes inside the pipe; a blocking version closes the bore. Confirm the marked pipe-size range and model rather than estimating compatibility from a photo.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| Mechanically expanded rubber test plug | Mechanical types expand a rubber seal by a screw, nut or lever; this type uses pneumatic inflation. |
| Male threaded pipe plug | Threaded plugs engage a female pipe thread. This interface seals by radial rubber contact inside the bore. |
| Inflation valve connection | The small valve feeds air into the bladder; it is a separate interface from the large rubber surface sealing the pipe. |
| Mechanical expanding test plug | A mechanical plug compresses its rubber seal with a screw or tightening mechanism; this plug expands by air inflation. |
| Push-fit pipe fitting | This is a temporary bore-blocking bladder, not a fitting joining pipe ends with a grab ring or fixed socket. |
Also called
Pneumatic pipe plugInflatable pipe stopperInflatable pipe test plugExpandable rubber test plugTest-Ball plug (Cherne trade name)
Good to know
This is a temporary closure interface, not a rigid pipe-fitting standard. “Male” is an interpretation of insertion geometry. The sample calls the rubber EPDM, but comparable Cherne listings say natural rubber; do not generalize the compound. Task dimensions were estimates and are not retained. Images show related sizes and shapes, not dimensional proof.
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