Impermeable filter

  1. I'm looking to buy a filter that will allow air to pass but not water. The problem is finding places online. Any suggestions? Thnx.
  2. jcsd
  3. mgb_phys

    mgb_phys 8,809
    Science Advisor
    Homework Helper

    An impermeable filter would be a bit pointless!
    Is this a medical or industrial application, what flow rate, what temperature range etc?
  4. Impermeable wasn't a good choice of words on my part. Impermeable to water to be specific. Temp range is between 0 and 100 degrees Celsius. As for flow rate....pretty much the best I can get as long as the water is kept from getting through. For medical vs industrial...I'll take anything I can get. As long as it won't break down when wet (like paper). I'm looking at porous plastics as a possibility right now.
  5. I am assuming you are referring to compressed air, as you don’t say. Water can be in air in more than one way. If it is in liquid form a filter will remove most of it, however if it is in vapor form, i.e. you are compressing air with a high relative humidly, you will need a dryer to remove it. You can get combination units that both filter and dry air. In the site below click on air filters and dryers for many manufacturers.
    What type of system you use depends on volume requirements etc.

    If you are getting a lot of water there may be something else wrong, like not draining tank etc. Here is a link with info on compressors:
  6. Thank you for the links.

    For application purposes, think of a water line that enters into a tank, then at the other side of the tank is the inlet (really the outlet for the tank) of another water line. At the top of the tank is an opening (vent) that has a filter such that when air and water pass into the tank, the air rises to where the filter is. The air that rises will be under some pressure as the water will be under pressure (transmitting of pressure undiminished and what not). The pressure will push the air through the filter but as soon as the air gets through and the water reaches the filter, the water can't get through. The flow rate through the filter need only be able to keep up with the incoming air. Such things can be fixed by using the right shape of filter, increasing the surface area (cylinder shaped filter of required length) to get the best flow possible. I suppose all I need to know is the micron size needed to do it (if it can be done at all).

    I know there are better ways of doing it (centrifugal force) but for the application I'm looking for, it can't be done any other way.
  7. It sounds like you are building a reservoir and if it’s built correctly; there should be no mixing of air and water, and no requirement for a filter to separate air from water.

    In case you do need a filter, there are absorbent filters that will remove the water. They are used to remove water from fuel and are often made from similar to diapers or personal hygiene products. One of the major suppliers like Parker should be able to help you.
  8. What I'm doing is actually looking to split water within a form of reservoir. The water once split will form oxygen and hydrogen gas. Rather than have the gas simply rise to a surface collection point, which depends on the apparatus being upright, I'm looking to have the gas get pushed through filters which the water can't pass. Provided the filters are located correctly about the reservoir, then orientation is no longer an issue.

    I got a call back from one of the companies I emailed inquiring about the filters. They couldn't help but suggested semipermeable membranes. I can't believe I never searched for such (or even thought of such) earlier.
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