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Don't use check valves on oxygen stones!

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  • Don't use check valves on oxygen stones!

    Title should read "carbonation stone"

    Recently we got a DO meter worth its salt (the Hach orbisphere), and found our FV DO readings to be unsightly high. Anywhere from 180-300 PPB even for beers that have not been dry hopped or the tank opened. Then I started thinking my only suspect would be the carbonation stone check valves we've been using. I replaced them all with SS plugs, and Viola! our tanks are reading the same DO as a 2 month old can of Coors now! Just a heads up for those without a DO meter. These are Check valves that we received with our stones when we bought them from GW Kent

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    Last edited by Junkyard; 03-27-2019, 03:58 PM.

  • #2
    Very interesting...we've got a handfull of these same check valves inline for various stones and other connections around the brewery, some from GWKent and some from Foxx. We've seen very low DO numbers in our BBT's (5ppb - 18ppb) on an AP CBox. Maybe you got a bad batch? Maybe we lucked out? Either way, I'll be investigating further! Thanks for sharing!



    • #3
      hey junkyard.
      If this is something that you have noticed across multiple batches and it stopped after removing the check valves, it sounds to me that you had a small leaks (probably in the tread tape) that was pulling air into the flow and thus into the stone/ tank. I highly recommend leaving the check valves in to prevent beer from backing into your co2 lines once the pressures equalize. Have you tried the blue tape? it has better chemical resistance than the regular white stuff and tends to hold up better to cleaning. if you have a pipe spool you can cap the end with the carb stone assembly in the other end, pressurize it and submerge it in a bucket of sani each time before use to check for leaks in the assembly.


      • #4
        also, if the stone assembly is plugged, how are you able to use them?


        • #5
          150-300 ppb was measured in a few batches since we got the DO meter. A couple of those being inexplicable- the tank wasn't opened at all. Then as soon as we switched to the plug it dropped to nearly nothing in a tank that had vanilla and fruit additions. I don't think the thread tape is the culprit because we used the same thread tape SOP for the plug as we did for the check valve.

          To use the stone with the plug we just take the plug out and quickly screw in a barbed fitting for now until we get some SS ball valves that are on order.


          • #6
            Where is your stone located that air can go in? When we've had CV problems with our Z&N stones, beer comes out.
            Timm Turrentine

            Terminal Gravity Brewing,
            Enterprise. Oregon.


            • #7

              So how would you explain how this happens? I ALWAYS use check valves with CO2 stones and never had problems. But I also always install a ball valve just upstream from them. Can't see how this arrangement would allow any O2 ingress. Or at least any more than standard butterfly valves, if not much less.
              Phillip Kelm--Palau Brewing Company Manager--


              • #8
                It sounds like you may be cold crashing without pressure in the tank. This would cause the tank to pull a vacuum, which would be equalized by pulling air through the check valve.

                Always cold crash with head pressure applied, and use a ball valve. The check valve is just a safety device, not sufficient to close off a tank.


                • #9
                  We always cold crash under pressure.

                  The stones are located halfway up the tank.

                  Not exactly sure how it was happening but my guess was a poor seal between the two pieces of the check valve body. I just measured another tank that we put a ball valve on instead of the check valve and it was 10 ppb.

                  I understand this could be limited to becoming a problem with our methods/conditions. I'm just happy to have figured it out and wanted to tell you guys in case some of you weren't able to test DO in your brewery .


                  • #10
                    Halfway up the tank?

                    Next time you get a BBT, make sure that the stones are very near the bottom. Halfway up is a poor design. Can't carbonate half batches, high chance of stratification, less hydrostatic pressure on the stone, shorter vertical column to dissolve curtain of bubbles, less effective convection through the bulk of liquid...... One way to help mitigate this shortcoming is to begin carbonation at a few degrees warmer than desired finished temperature and let the thermal convection help roll the contents.

                    BTW, Ambrosia hit an important nail: The check valve is insufficient to close off a tank. It is meant to keep liquid out of the carbonation line. If it is the only means of tank shutoff, then oxygen could find a way in. Just because you have CO2 pressure on the tank does not mean the valve is sealed. Partial pressure of O2 is very, very low in the tank. Outside it is very high. That itself could cause O2 to migrate inside.

                    Best of luck!
                    Phillip Kelm--Palau Brewing Company Manager--


                    • #11
                      From now on buy your stones and assembly from Zahm Nagle. Worth the money.

                      Also teflon tape is Not a sealant, its to prevent galling of the threads and also to allow the fitting to be removed. Because of this it does allow you to turn the fitting in more, so better seal - but not its intended purpose. There is thread sealant tape, what Ive used before is baby-blue.

                      Congrats on the DO meter Corey!
                      Brewmaster, Minocqua Brewing Company
                      "Your results may vary"


                      • #12
                        The only way I see oxygen going into a pressurized tank via a stone port is via the venturi effect of oxygen while you are pushing CO2 into the stone. Hmm.
                        Joel Halbleib
                        Partner / Zymurgist
                        Hive and Barrel Meadery
                        6302 Old La Grange Rd
                        Crestwood, KY


                        • #13
                          Philip- that made sense to me too, laws of osmosis and concentration gradients, oxygen finds its way in any place you allow it to, and the check valve assembly was the weakest link

                          Ted- I'll tell Corey you said Hi, also my mistake I was saying Teflon tape but Im sure it is actually thread sealer.


                          • #14
                            Teflon thread seal paste

                            Got ours from foxx i think. Seemed safer than plumbers pipe dope, although that should be fine too if its for water lines. Definitely gets things sealed up solid. NSF.