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  • Air cooling unit drain

    I live in a high rise condominium. It has 16 floors. On the roof is a cooling unit (180 ton) whose 2-in condensate drain terminated in one of the vent stacks. It was installed by a "reputable" plumbing company approximately 15 years ago and now the cast iron vent stack has begun developing cracks. Several units have mold in the walls due to the cracked vent pipe.

    My question is this: Is it legal to dump condensate into a vent stack? I thought that vent stacks couldn't have water draining in them so that the regular waste lines from sinks and other fixtures would be able to function properly.

    There is an adjacent waste stack a couple of feet away. Would it be ok to have the condensate drain into that if it had an airbreak?

    Our HOA has no clue nor does the property management company that services our building on what to do.

    I thank you in advance for your responses. I hope to be able to get educated here so that we can talk intelligently to a plumbing company on how to resolve the problem.

  • #2
    Re: Air cooling unit drain

    Was wet venting allowed there 15 years ago? (I would think what they did was clever and perfectly acceptable.)
    Can the condensate drain be terminated near a roof drain instead?
    I'd take an educated guess - but I'm unqualified.
    It ain't just soot, it's paydirt.
    "I swear, wherever Gift goes, argument follows." -Youtube comment

    Comment


    • #3
      Re: Air cooling unit drain

      Originally posted by franklie ing View Post
      I live in a high rise condominium. It has 16 floors. On the roof is a cooling unit (180 ton) whose 2-in condensate drain terminated in one of the vent stacks. It was installed by a "reputable" plumbing company approximately 15 years ago and now the cast iron vent stack has begun developing cracks. Several units have mold in the walls due to the cracked vent pipe.

      My question is this: Is it legal to dump condensate into a vent stack? I thought that vent stacks couldn't have water draining in them so that the regular waste lines from sinks and other fixtures would be able to function properly.

      There is an adjacent waste stack a couple of feet away. Would it be ok to have the condensate drain into that if it had an airbreak?

      Our HOA has no clue nor does the property management company that services our building on what to do.

      I thank you in advance for your responses. I hope to be able to get educated here so that we can talk intelligently to a plumbing company on how to resolve the problem.
      the amount of condensate from an AC is not nearly enough to cause the waste line to not function as intended. heavy rain causes just as much. also, the ac condensate did not cause the pipe to fail. if it was condensate from a heating system, then it's probable, but not from AC.
      ~~

      ... it was plumbed by Ray Charles and his helper Stevie Wonder

      Comment


      • #4
        Re: Air cooling unit drain

        The waste line isn't a problem, It is the vent stack that is supposed to be dry which is getting wet. I was thinking that the wetting up and drying down of the pipe would excaerbate the cracking problem. In addition, all of the vent 'Y"s from the individual residential units have the wrong direction and would preferentially drain the water into the vent piping of those units.

        I don't believe wet venting would be allowed for the condensate drain of a 180 ton cooling unit by the UPC/CPC, would it?

        Does the Code allow a condensate pipe to empty into a roof drain?

        Comment


        • #5
          Re: Air cooling unit drain

          I'd ask how you know the difference between a vent stack, and a waste stack on the roof.....If a pipe from the plumbing system is open-ended through the roof ,it's a vent.....period. The piece of pipe between the highest fixture in the building and the part that's open on the roof is the "stack vent", "vent stacks" are stacks through a building that serve venting purposes only, and can be tied in to the "stack vent" before penetrating the roof(or vice-versa) to save some penetrations in the roof membrane.

          Arguing that the failure occurred because those pipes weren't supposed to get wet ,that makes no sense, it's pipe ,it's meant to convey water...and air. There are no special pipes that I'm aware of ,"That can't get wet" or they'll fail.

          Cooling condensate is not considered harmful to pipes in an untreated form....Combustion condensate, on the other hand, is quite detrimental to some pipes.

          Should the condensate from a 180 ton unit just be piped down a random pipe sticking through the roof?...probably not. However, the code(mine is IPC) only states that cooling condensate should be disposed to an "approved place of disposal". And that could mean anything....a roof drain, or some pipe sticking up through the roof, it would depend on what the inspector allowed at that time ,on that day ,in your jurisdiction.

          I would say you'd have a case if your complaint had to do with the fixtures attached to that system ,not operating properly due to improper venting...i.e. slow drains, gurgling sounds from the traps, things like that,......not failure of the pipe itself...that would just be defective pipe.

          Comment


          • #6
            Re: Air cooling unit drain

            Originally posted by Plumberinthebuff View Post
            I'd ask how you know the difference between a vent stack, and a waste stack on the roof.....If a pipe from the plumbing system is open-ended through the roof ,it's a vent.....period. The piece of pipe between the highest fixture in the building and the part that's open on the roof is the "stack vent", "vent stacks" are stacks through a building that serve venting purposes only, and can be tied in to the "stack vent" before penetrating the roof(or vice-versa) to save some penetrations in the roof membrane.

            Arguing that the failure occurred because those pipes weren't supposed to get wet ,that makes no sense, it's pipe ,it's meant to convey water...and air. There are no special pipes that I'm aware of ,"That can't get wet" or they'll fail.

            Cooling condensate is not considered harmful to pipes in an untreated form....Combustion condensate, on the other hand, is quite detrimental to some pipes.

            Should the condensate from a 180 ton unit just be piped down a random pipe sticking through the roof?...probably not. However, the code(mine is IPC) only states that cooling condensate should be disposed to an "approved place of disposal". And that could mean anything....a roof drain, or some pipe sticking up through the roof, it would depend on what the inspector allowed at that time ,on that day ,in your jurisdiction.

            I would say you'd have a case if your complaint had to do with the fixtures attached to that system ,not operating properly due to improper venting...i.e. slow drains, gurgling sounds from the traps, things like that,......not failure of the pipe itself...that would just be defective pipe.
            Plumberinthebuff, thank you for your response. From what I understand the California Plumbing Code (CPC) is based on the Uniform Plumbing Code (UPC). According to the UPC "Indirect waste piping shall discharge into the building drainage system through an airgap".

            the building drainage system is NOT the same thng as the building waste system, is it?

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            • #7
              Re: Air cooling unit drain

              ~~

              ... it was plumbed by Ray Charles and his helper Stevie Wonder

              Comment


              • #8
                Re: Air cooling unit drain

                Click image for larger version

Name:	72fed055bd4867ca3f562e978d259245.jpg
Views:	1
Size:	113.6 KB
ID:	18037 This picture is the front of the cooling unit showing the drain lines.

                Click image for larger version

Name:	cc3e3ae35a1dc8953b3de9612edced53.jpg
Views:	1
Size:	103.6 KB
ID:	18036 This picture is the drain line draining onto the roof now because a plumber rotated the trap 180 degrees away from the drain. The same plumber ran a video camera down the vertical pipe and said it was a vent stack because of the direction of the 'Y's that tie into the stack.

                Comment


                • #9
                  Re: Air cooling unit drain

                  the building drainage system is NOT the same thng as the building waste system, is it?


                  Those terms are not generally used in the plumbing lexicon.........Buildings have a sanitary system, and a storm system...... or possibly a combined system. That depends on the locality. A "Building Drain" is defined as the lowest part of a drainage system that receives the discharge from soil, waste and other drainage pipes inside and extends to 30 inches beyond the exterior of a building, at which point it is then referred to as a building sewer.


                  Again, this condensate probably could have been run a different way....I can't say weather your locality requires clear water wastes to go to storm or sanitary (In my neck of the woods, depending which municipality your dealing with, it can go to either)...but to me that's a moot point....


                  You just can't use the argument ,the pipe failed because it wasn't supposed to get wet.The reason those "WYE's" are in the direction they are ,is to route any "water" down through the vent pipes to end up in the "building drain", the vent system is piped with the complete expectation that water will run through it. That's why code states " all vent pipes shall be graded and connected as to drain back to the drainage pipe by gravity", its completely expected those pipes will see water...... by either condensation, rain water....or hack plumbers.


                  If you feel the pipe failed prematurely, you'd have to look into the pipe manufacturer's warranty...and btw..... Charlotte pipe's DWV cast iron warranty is 5 years...good luck with that.

                  Comment


                  • #10
                    Re: Air cooling unit drain

                    As long as it's just AC water -

                    I dont even see the need for the trap as the exit of the vent is right there.

                    why not either dump it onto the roof near the unit or install a trap near the unit (make sure it has clean outs) and extend the pipe to the nearest roof drain (with air gap)? And remove the restriction on that vent pipe, it cant possibly be good for the building.
                    ~~

                    ... it was plumbed by Ray Charles and his helper Stevie Wonder

                    Comment


                    • #11
                      Re: Air cooling unit drain

                      Originally posted by Plumber Punky View Post
                      As long as it's just AC water -

                      I dont even see the need for the trap as the exit of the vent is right there.

                      why not either dump it onto the roof near the unit or install a trap near the unit (make sure it has clean outs) and extend the pipe to the nearest roof drain (with air gap)? And remove the restriction on that vent pipe, it cant possibly be good for the building.
                      I agree with what you wrote about venting that I have put in bold.

                      The trap is a requirement of the UPC if the drain line is more than 5-ft in length.

                      The problem with using the roof drains is that roof drains drain onto the deck of the penthouse suite of the building and then is collected into drains that dump into the street curb which goes into the city storm drain system in the street. The deck sees pedestrian traffic.

                      what do you mean about "installing a trap near the unit"?

                      BTW, thank you for responding to my posts.

                      Comment


                      • #12
                        Re: Air cooling unit drain

                        residential ac units have a trap in the condensate drain line next to the unit. do the same with your commercial unit so that no sewer smells can get sucked in (if it's on the negative pressure side of the blower). then just dump the drain line anywhere - on the roof, over the edge, or into a roof vent.

                        unless you're flooding the deck and people are getting wet, what's the problem? water is water...and this is CLEAN water. what happens when it rains and why is this not a problem? the only major issue I see is condensation on the outside of the pipes caused by cold condensate water.

                        the trap, as pictured, would be a requirement for an indirect waste line with an air gap.

                        our other CA plumbers may have more insight on local codes that apply to condensate water.
                        ~~

                        ... it was plumbed by Ray Charles and his helper Stevie Wonder

                        Comment


                        • #13
                          Re: Air cooling unit drain

                          An off the wall question: would the vent with the the reduced diameter on the wye cause a toilet bowl to be sucked dry? would that also cause pressyre swings in the vent and connected waste stack?

                          My neighbor who is on the that waste and vent stack commented to me that his toilet every once in a while is getting the water sucked into the waste line and then his bathroom fills up with sewer smells.

                          I asked the building handyman to remove the trap to see if that would improve his situation. He was reluctant because he isn't a plumber but he finally did it.

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                          • #14
                            Re: Air cooling unit drain

                            it might if there was a large amount of water drawn on the other waste stacks and there wasnt enough venting. air then enters the least resistive access point, sometimes a toilet bowl, and the water is carried into the drain with the air. the dropped water breaks the trap seal.
                            ~~

                            ... it was plumbed by Ray Charles and his helper Stevie Wonder

                            Comment

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