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  • Air pressure vs. Water pressure

    Just curious, Say on 200 psi. Threaded connections,would one be prone to leak over another ?
    I can build anything You want , if you draw a picture of it , on the back of a big enough check .

  • #2
    Re: Air pressure vs. Water pressure

    i believe that the water molecules would show a leak faster than air.

    air pressure would pretty much be equal at the elevation of the pipe, yet water pressure will change .43 pounds per foot.

    water would be safer to test with than air pressure if something were to blow. air compresses while liquid doesn't.

    don't go blowing yourself up tool

    rick.
    phoebe it is

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    • #3
      Re: Air pressure vs. Water pressure

      Might be a fun demonstration. I'll give it a try when I get back from vacation.

      Ok, I just googled size of an air molecule and started reading and............................screw that, who cares
      sigpic

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      • #4
        Re: Air pressure vs. Water pressure

        Air is the smaller molecule it will leak first. Is my guess.

        Water is a safer medium to test with as it does not hardly compress, when a rupture happens it is immediately relieved and there is no stored energy in the medium. as with air if a rupture happens there is a lot of stored energy in the air to continue to expand,

        super heated water is much worse yet as the water turning to steam is explosive. huge amounts of stored energy.



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        • #5
          Re: Air pressure vs. Water pressure

          Today I made up a fitting assembly for My pressure washer. My p. Washers and air compressors have same quick disconnect fittings. Washers are at shop I was home and had a air compressor here. So this came to mind. I had a feeling it would be of interest. Good job for the Young Minds at Your school Master.
          I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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          • #6
            Re: Air pressure vs. Water pressure

            tool, just be sure you have a proper relief valve and an adjustable unloader if you plan on using your pressure washer to pump up piping. it can get out of control faster than you think.

            rick.
            phoebe it is

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            • #7
              Re: Air pressure vs. Water pressure

              Originally posted by PLUMBER RICK View Post
              tool, just be sure you have a proper relief valve and an adjustable unloader if you plan on using your pressure washer to pump up piping. it can get out of control faster than you think.

              rick.
              Thanks. Crazy, YOU BETCHE ! Not that crazy !
              I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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              • #8
                Re: Air pressure vs. Water pressure

                I can tell you that on a suction line of a shallow well pump, and air leak small enough to not allow water out under pressure is enough of a leak to keep the pump from priming in many instances. Air is definitely the smaller molecule.

                What did Mythbusters pump that tank up with? Air or water?
                Frequently asked questions about pumps and tanks.

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                • #9
                  Re: Air pressure vs. Water pressure

                  That be the result of superheated water being released to the atmosphere. Normally the condition can be caused by plugging off the relief valve and disabling the thermostats. Watts Company was running those tests and filming them as far back as the early 1940's Why Mythbusters decided to do a show on a subject that has been proven many times is beyond me but I suppose that blowing crap up always makes for good TV
                  sigpic

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                  • #10
                    Re: Air pressure vs. Water pressure

                    Ok, I saw they watching a digital readout. They said that was the pressure which was twice the rated max pressure. So that was the result of heating the water. Nasty!
                    Frequently asked questions about pumps and tanks.

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                    • #11
                      Re: Air pressure vs. Water pressure

                      Originally posted by speedbump View Post
                      I can tell you that on a suction line of a shallow well pump, and air leak small enough to not allow water out under pressure is enough of a leak to keep the pump from priming in many instances. Air is definitely the smaller molecule.

                      What did Mythbusters pump that tank up with? Air or water?
                      Thanks Speed. That answers it.
                      I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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                      • #12
                        Re: Air pressure vs. Water pressure

                        Doesn't water expand 1742 times when turned to steam or somewhere around that number.

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                        • #13
                          Re: Air pressure vs. Water pressure

                          Originally posted by PLUMBER RICK View Post
                          i believe that the water molecules would show a leak faster than air.

                          air pressure would pretty much be equal at the elevation of the pipe, yet water pressure will change .43 pounds per foot.

                          water would be safer to test with than air pressure if something were to blow. air compresses while liquid doesn't.

                          don't go blowing yourself up tool

                          rick.
                          Wow Rick one of the few times I have to disagree. Air being the smaller molecule will absolutely leak first. Although when you say "shows"... clearly water will "show" first since air doesn't "show" being invisible and all. You're right on the head pressure variations of course, but I don't think that's what the original question was really wondering. I personally have seen many times where air will leak when water won't.

                          Speaking of liquids not compressing but gases compressing... When I was in the Navy our sub had high pressure steam. I don't know if the Navy makes the exact PSI public but the pressure was really really high. If there was a steam leak we were instructed to search for the leak using broom handles or you would lose a hand, arm, or whatever the steam leak hit. Cut and cauterized in one shot. (Glad I didn't work in the engine room )
                          Time flies like an arrow.

                          Fruit flies like a banana.

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                          • #14
                            Re: Air pressure vs. Water pressure

                            Originally posted by geno gardner View Post
                            When I was in the Navy our sub had high pressure steam. I don't know if the Navy makes the exact PSI public but the pressure was really really high. If there was a steam leak we were instructed to search for the leak using broom handles or you would lose a hand, arm, or whatever the steam leak hit. Cut and cauterized in one shot. (Glad I didn't work in the engine room )
                            Actually, submarines use a very conventional steam system....600 psi nomimal, lower at most points in the system. The old story about searching for steam leaks with a broom handle is for surface ships with 1200 PSI steam. On 600 psi or less, you do see the steam . It is the reactor which operates at much higher pressures but it is in a sealed compartment where "no man has gone before"

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