The Cherne I-Series Test-Ball 4"-8" (part #310-088) is a premium multi-size pneumatic blocking plug covering 4" through 8" sewer and storm pipe. Rated for 15 PSI at 45 PSI inflation. Premium natural rubber mechanically bonded to aluminum end plates with full body cording for maximum durability. Multi-size coverage eliminates carrying separate plugs for each diameter. Usage range 3.95"–8.25" ID.

Key Features

I-Series premium construction — natural rubber bonded to aluminum end plates with full body cording
Multi-size coverage — one plug covers multiple pipe diameters
15 PSI / 35 ft. head — rated for sewer air pressure testing
Full blockage — complete shutoff, no bypass
3/4" eyebolts + field-replaceable pressure relief valve (larger sizes)

Technical Specifications

Cherne Part Number	310-088
Pipe Size Range	4"-8"
Usage Range (Pipe ID)	3.95–8.25"
Bypass	None (full blockage)
Max Back Pressure	15 PSI / 35 ft.
Inflation Pressure	45 PSI
Body Material	Premium natural rubber, aluminum end plates
Deflated Length	~23"
Operating Temperature	0°F to 125°F

Applications

Municipal sewer air pressure testing, storm drain isolation, large-diameter pipe blocking during construction and repair, and compliance testing on trunk mains. Deploy through manholes using eyebolts and poly-lift line. Always follow Cherne inflation and back-pressure guidelines — never exceed rated pressures.

Questions on sizing or bulk pricing? Call (866) 514-3684 or email us — same-day shipping on in-stock items, tax-exempt purchasing for qualified accounts.

Cherne ® I-Series Test-Ball ® Blocking Plug 4-8 in, 15 PSI