Sewer Air Test Plugs

Cherne® High Pressure-Plugs’ optimized design using steel, aramid and natural rubber ensure longevity through its robust construction, when high back pressures exist. Cherne I-Series Plugs have a smaller deflated diameter and shorter overall length that make it easier to insert through tight man-hole openings. All I-Series Plugs feature our Patented Field-Repairable Ruptured Disc Technology, which eliminates the risk and danger of over inflation due to faulty gauges or user error. 

Frequently Asked Questions

What is the shelf life for Cherne pneumatic plugs?

Cherne offers a 2 year warranty on all pneumatic plugs from date of manufacture, (plugs are post-dated by six months to allow for shelf time). If kept in controlled conditions (not exposed to sunlight and kept at temperatures between 0-125 degrees F) the pneumatic plugs remain in good condition for a longer period of time. Plugs should always be inspected for visual damage prior to every use.

What type of rubber is a Cherne pneumatic plugs made from?

All of Cherne’s pneumatic pipe plugs are made from natural rubber. The only exception is our yellow pillow plugs which are made from a polyurethane impregnated fabric.

How often should a pneumatic plug pressure be checked?

Inflation pressure should be checked a minimum of once every 4 hours while a pneumatic plug is in use.

How long can a Cherne pneumatic plug be expected to stay in good condition?

This answer depends on how the plug is maintained. If the instructions are followed in the Cherne Safety Instruction Manual, it is not unusual for the plug to last for many years. If the instructions are not followed, a plug can be destroyed during the first use. Cherne pneumatic plugs come with a 2 year warranty from date of manufacture.

Why is it important to know pounds of force calculation?

This calculation is important to the end user and helps them understand the forces behind the plug so that they can decide the proper way block the plug.

What is the formula to calculate backpressure?

Backpressure is defined in PSI (pound per square inch) or feet of head.  Simply read the gauge pressure for PSI.  For feet of head, calculate height of water over the centerline of the plug.  Example; 100’ line at 1% slope with a 10’ manhole (100 x .01) + 10 = 11 feet of head.  

What is the definition for feet of head?

Feet of head is the height of water over the center line of the plug.

Which inflatable plugs are repairable?

There are patch kits available for Urethane plugs. Other plugs that can be patched or have the bag replaced, are as follows; 15”-30” / 24”-42” / 20”-40” / 24”-48” / 24”-60” / 48”-72” and 54”-96”.

What size plugs is repairable and which plugs are not repairable?

Generally speaking pneumatic plugs that do not have sealing rings may be eligible for patching. The damage to the plug cannot be any longer than 4 inches, or deep enough to penetrate the cording. Plugs cannot be patched more than 4 times. Other repairs can be made as well, like replacing inflatable bladders, bypass hoses, castings and fittings. When in doubt, ask the customer to take a few digital pictures of the damaged area and email it to you. Forward the pictures by email to the Cherne QA Department along with a brief description of the damage for final determination.

Can Cherne plugs be used on elliptical pipe?

Yes. Cherne publishes a chart that pairs up our pneumatic pipe plugs with some of the most popular sizes of elliptical pipes.