How many PSI do I need to get 2CFM?

  1. The project that Im working on.
    I am aerating a pond with an air stone diffuser. The diffuser requires 2 CFM of air flow to work optimally.
    Im feeding this diffuser with 1/2" pvc line at a distance from compressor to stone is approx. 200 feet.

    The stone is placed 10 feet deep under the water.
    At what psi would in need to set my regulator to maintain an even volume of 2 CFM to my diffuser.
    This will help me size my compressor which is what im trying to do. If the answer is X psi then when I hook it up I need to keep sizing my compressor up until it can generate enough air to over overcome X psi and overcome the amount of air being released into the line through my regulator. Hope this question makes sense.
  2. jcsd
  3. Baluncore

    Baluncore 3,305
    Science Advisor

    Welcome to PF.
    There will be a small pressure loss in the pipeline and some in the stone but the most significant pressure requirement is the hydrostatic pressure at 10 feet, which will be about 5 psi.
  4. Thanks. That answers part of my question. I'm pretty sure that whatever air compressor/pump I use, will be able to produce pressures well over that to overcome the weight of the water. I'm more concerned with being able to push enough volume(cfm) of compressed air to my stone diffuser.
    The fish experts say that I need 2 cfm of air being pushed through the stone.
    So, without using some sort of fancy meter that I would have to install inline that could read air flow in cfm, I'd like to know if there is some formula that could give me my answer.
    Something that would say, you need to set your regulator @ ?psi to achieve a flow of 2cfm at the end of your 200' long 1/2" PVC line that is 10 foot under water.
  5. Baluncore

    Baluncore 3,305
    Science Advisor

    I think you need to regulate flow rather than pressure.
    Maybe you should consider a fixed displacement air pump running at a fixed speed.
    There are many choices, consider a vane, gear or piston pump. If possible, lubricated with water.
    That will be most energy efficient since there is no regulator.
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