Drainage Venting. What do you think?

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    • #279819
      Carol Shikany

      G,day guys,

      Does the vent on a drainage line (DWV in ground) HAVE to be the second last fixture? I was always under this impression, until i went back to TAFE to do additional courses, and during the design work part i noticed in the teachers example that the vent was not the second last fixture, in fact it was a stack (which i know u can use as a vent), and there was at least 3 junctions after it.

      When i enquired about this he explain that the vent has to be no more that 10mtrs from the end of the line, which in the design it was. Not the second last fixture, though closer to the end the better.

      Most plumbers tend to agree that the vent has to be the second last.

      So which one is it? Second last or 10mtrs from end of line?

      An example of this is a vent between a junction for a WC and the end of a line which goes from external to internal drainage and picks up a shower, floor waste, laundry tub and kitchen sink.

      In this example the vent is not necessarily the second last fixture as the 88 deg bend after it goes inside to pick up 4 fixtures, but is well within the 10mtrs of the last fixture being the kitchen sink.

      If the vent had to be the second last fixture i would have had to of brought a vent line back to the outside of the house to rise up or make a duct in the corner somewhere and go through the roof.

      Interested in your replies!

      r3vhead

    • #301752
      kenny b

      “Does the vent on a drainage line (DWV in ground) HAVE to be the second last fixture?”

      Drainage lines in the ground don’t require vents.

      “in fact it was a stack (which i know u can use as a vent)”

      A stack is a general term, you need learn the difference between a soil stack, waste stack, stack vent and vent stack.

      I believe your refering to the venting arrangement of a circuit vent or loop vent that is connected to the top half of a horizantal branch between the last two fixtures.

      “Most plumbers tend to agree that the vent has to be the second last.”

      Most plumbers today are not real plumbers.

      Sorry if I sound harsh, but it’s like nails on a chaulk board to me. I haven’t been around for a few years but recently refound the site.

      Where have all the plumbers gone? I see one maybe two.

      kenny b

    • #301753
      r3vhead

      I don’t know what State or Country you reside in, but here is NSW Australia, ALL drains require a vent especially the one i described in my original post which was house drainage.

      I know the difference between soil, waste etc stacks, but there was know need to elaborate due to the fact that pretty much all stacks, whether it picks up 50 storeys, a two storey cottage or just a hand basin, it must vent to atmosphere to assist in the drainage and well as prevent any siphonage.

      The stack that i mentioned was a soil stack on a 2 storey cottage.

      All in all, the question that i asked was not answered.

    • #301754
      kenny b

      “All in all, the question that i asked was not answered”

      That’s because your question only makes sense to you, your lacking the correct terminology that defines your question. You’re making general statements that are just not true or correct.

      Here is your original question:

      “Does the vent on a drainage line (DWV in ground) HAVE to be the second last fixture?”

      Applicable drainage lines of your question- building drain, horizontal branch of the building drain, horizontal branch, fixture branch or fixture drain. The latter contains a single fixture which only makes your question even more confusing.

      I didn’t stop in to give you a hard time, and of course local codes prevail, but real plumbing actually has a common language. It’s just getting lost because it’s easier to dumb it down in today’s world than to learn the correct way.

    • #301801
      Selgas

      Not al all sure I fully inderstand your original question however I will endeavour to assist you with the following ::: AS/NZ 3500 Part 2.2 Clause 3.9.1(b) states amoungst other things… In a non boundary trap area a minimum of 50mm vent is required to be provided at the upstream end on the drain, between the last and the second last fixture, but no further than 10 metres from the end of the main vented drain, or in the case of a gully installed on the main drain the distance from the gully to the vent should be no further than 10 metres.

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