Advantages of an Air Diaphragm Pump
Soft Start (low psi and low flow for start-up)
With soft start, the flow AND pressure are very easily controlled. You can pump a few tablespoons at a slow, low pressure until you see that everything is correct. Then crank up flow by giving it more air.
In contrast, with a gear pump/electric motor, the pressure and flow start immediately/violently because a gear pump is a positive displacement pump. That means that for every revolution of the pump, a defined amount of liquid MUST come out of the pump—every revolution! And the outlet pressure is relatively MUCH higher. Because of this, there is no forgiveness if something is not hooked up correctly or some valve is not set right.
Easily Controlled Pressure (in filter chambers)
As the filter press fills with DE and reduces or stops flowing, it’s very simple to twist the regulator knob up a bit to resume pumping. This can be done at any time, at any flow rate, from stopped to almost wide open. Of course, this is dependent on having an air pressure regulator in-line between the air compressor and the diaphragm pump.
Variable Flow (less air pressure for less flow, increase air pressure for more flow)
If you are pumping filtered syrup into your canner while you are filling small bottles, you can turn the pressure down low and slow. On the other hand, if you are filling barrels or 5 gallon containers, turn up the air and let it rip!
Harmless Stall (if/as filter plugs)
A HUGE advantage of air pump versus electric motor pump is that the air pump can remain “stalled” for hours (days!) without harm to your equipment. Try that with an electric motor driven pump!