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Concrete pipe is porous and the ASTM guidelines give allowances for this porosity. 

Owner’s Manuals and parts lists on all Cherne equipment can be located in the technical section of the Cherne website. “pieces parts” – replacement parts for the hydrostatic test pumps and joint testers. We do not stock engine parts.  


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.

Backpressure is measured either in terms of feet of head or psi.  

  • Feet of Head. Simply stated “feet of head” is the height of water above the centerline of a plug. For vertical pipe the calculation is easy. Simply measure the height of the pipe and that is the footage of head pressure. For horizontal pipe, feet of head is still simply the height of water above the plug. There are various ways to determine this height base on knowledge of the actual application. For example, if you have a 300’ long section of pipe at a 1 degree slope, the feet of head is 3’. (300*.01)
  • PSI - This measurement is typically done with a pressure gauge.
  • #’s (pounds) of Force. This is the calculation to determine how much force is being held back by a plug. It is useful information when trying to design a plug blocking system for a specific job.
    • Calculating pounds of force for air pressure tests.  
      • PSI *square inches of pipe opening = #’s of force
        • Example:  8” and 5 psi test.  Pipe area = Pi R2 * (3.14*42=.50.24”).  50.24” * 5 PSI = 251.2 #’s of force.
    • Calculating pounds of force for head pressure applications.
      • Convert Feet of Head to PSI and then do calculation above.
        • PSI = Feet of Head *.434.
        • Example:  8” pipe at 30’ of head.   Pipe area = Pi R2 * (3.14*42=.50.24”) 30 Feet of Head *.434 = 13.02 13.02 * 50.24 = 654 lbs. of force.

One foot of head to psi conversion chart is attached for your reference.  Feet of head psi ratings for each Cherne plug can be found in the Cherne catalog.

10 inches

Smoke bombs have a one year shelf life from the date of manufacture. 

Diaphragm Hydrostatic test pumps use oil in the engine, in the gear reduction unit, and in the pump itself. 30 weight motor oil is used for the engine and pump. The gear reduction unit uses 90 weight gear lube.

  • **Piston Pumps only use oil in the engine.  (30 weight motor oil.)

All of Cherne’s hydrostatic test pumps are designed to pressure test new potable water lines. Piston style pumps can be pressure fed or suction fed. 

  • Piston pumps cannot be run dry nor should they be used in conjunction with chlorine. (Chlorine is frequently used when new potable water lines are being tested to avoid contamination). 
  • Diaphragm test pumps cannot be pressure fed. However they can be used with an optional gravity feed water tank sold by Cherne, or with a large container (like a garbage can) filled with water into which the intake hose can be placed. 

Diaphragm pumps can be used with up to a 10% chlorine solution in the test water.

No. Field Scrapping products should only be defined by plumbing product manager.

Material Safety Data Sheets for smoke bombs and liquid smoke can be found in the technical information section of the Cherne website at or    

Cherne offers two poly lift lines. The poly lift line with inflator (Schrader) valve fittings can be used on any plug that has an eyebolt, and also has a inflator valve. The poly lift lines with gauge can be used with any plug that has an eyebolt, and also has a removable inflator valve fitting. 

Yes. The #012678 Tub Plug Set. 

Yes. the Iron Grip Plugs can be used for this application and comes in sizes 2”, 3”, 4”, 6”, 8”, 10” and 12.”

Both pipes have the same outside diameter. SDR 35 has a thinner wall that SDR 26.

Yes. Cherne offers the T-Handle Gripper as a flow through plug. 

Mechanical plugs can be used to block an opening (Grippers are mechanical plugs). Be sure to use the correct size Gripper for the opening.

Gripper plugs have natural rubber O-Rings. These O-Rings allow for operating temperatures between 0° F to 125° F. Consult engineering for usage outside this temperature range.

Yes. Cherne offers two chemical resistant mechanical plugs: The Cherne Well Monitor Plug and the Cherne Petro Econ-O–Grip.

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.

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.

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.

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

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”.

The bypass cap or plug is removed and replaced with an Air Loc Conversion Kit.

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

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.

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

Both our original long ball and our MS2 Long Balls are designed to seal wye fittings while conducting a sewer test. The MS2 Long Ball is unique as it features a relief valve, is multi-size, and inflates and deflates in stages to keep the work area dry by keeping the water from coming up through the pipe riser during the deflation process.