Example (use metric units when applicable):
Using an 18” bladder pump and 0.17” I.D. tubing, what size compressor is recommended
to purge a sample 200’ deep?
Step 1: Determine air consumption per cycle.
In this case the 1.66 BP 18” pump is used with 200’ of 0.17” I.D. tubing.
Volume of tubing = 30 in³ * 2 = 60 in³
Volume of pump = 39 in³
Total air consumption per cycle = 60 in³ + 39 in³ = 99 in³
Step 2: Determine air consumption per hour.
Assuming the pump cycles no more than 6 times per minute, we can estimate maximum
air consumption per hour.
99 in3/cycle * 6 cycles/min * 60min/hour =35,640 in3/hour or 21 ft³/hour
If you plan to use an air compressor, we advise that you use one with a reserve tank to
insure proper air supply to the pump. If you plan to use a Nitrogen Tank, see Figure 2.1 for
Nitrogen Tank Volume vs. Bladder Pump consumption.
Determining PSI
Determine the air pressure needed to operate the Bladder Pump based on the length of
the air supply line to the pump (well depth).
Use this simplified formula:
0.5 PSI (per foot) + 10 PSI (to account for tubing friction) = required PSI
0.12 bar (per meter) + 0.7 bar (to account for tubing friction) = required bar
Example (use metric units when applicable:
For a pump 400 ft. away from the air source
(400 ft. * 0.5 PSI) + 10 = 210 PSI
As mentioned above, the additional 10 PSI/ 0.7 bar is to account for the pump itself and
friction loss along the airline tubing. When the length of the airline is 50 ft./15 meters or
less, there is no need for the additional pressure.
To determine minimum operating pressures for the specific Bladder Pump model you are
using, consult the pump’s specifications. Typically, the minimum operating pressure will be
5 PSI/ 0.4 bar above static head.
