Wet vent a bath group, UPC Code

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Rjohnson, Oct 21, 2013.

  1. Rjohnson

    Rjohnson New Member

    Messages:
    4
    Location:
    Mn
    Wondering if anyone has input on this diagram of a potential bathroom plumb job? In particular, the wet venting of the shower. Would that work? I am under some pretty tight constraints.

    Thanks!

    Attached Files:

    Last edited by a moderator: Oct 21, 2013
  2. Terry

    Terry Administrator Staff Member

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    The shower is not vented in this drawing. You will need to add a vent before it enters the main line.

    The toilet being flushed will siphon the shower.
  3. Rjohnson

    Rjohnson New Member

    Messages:
    4
    Location:
    Mn
    Just for my own learning, isn't the 3 inch horizontal line and the short section of 2 inch vertical line considered a wet vent?
  4. Terry

    Terry Administrator Staff Member

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    Not for the shower. No.
    The shower will need a vent.
    The lav can wet vent a shower if it's run in 2", but you can't run a toilet past the shower without sucking all the water out of the trap.
    The shower will need a vent "before" it enters the line where the toilet is.

    Pull a permit, and the inspector will be glad to look at this.
  5. hj

    hj Moderator & Master Plumber Staff Member

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    Technically, you are draining a "major" fixture over/past a "minor" one and that cannot be done unless the minor fixture has its own vent. Your two sinks are also be improperly vented unless you have a "lenient" inspector.
  6. Terry

    Terry Administrator Staff Member

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    Gosh. I was so worried about the toilet I didn't notice the lav running by the other lav without a vent!
    That has to be changed too. Consider using a fixture cross for the two lavs with a vent up the middle of them.

    [​IMG]
    Last edited: Oct 22, 2013
  7. Rjohnson

    Rjohnson New Member

    Messages:
    4
    Location:
    Mn
    Got it. This is what I'm picturing now. The transitions would be wyes. A cross tee for the lavs.

    Attached Files:

  8. Tom Sawyer

    Tom Sawyer In the Trades

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    IPC would allow it.
  9. Terry

    Terry Administrator Staff Member

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    But his inspector uses UPC

    That and when plumbing is done the IPC way, it affects the other fixtures more than it should.
    I wouldn't plumb my home IPC no matter where I was living.
    In UPC land, I'm used to plumbing fixtures working well "all" the time.

    I get it though. My ancestors landing in Plymouth early 1600's
    The plumbing wasn't much then either.
  10. Rjohnson

    Rjohnson New Member

    Messages:
    4
    Location:
    Mn
    So what would be different in upc?
  11. Winslow

    Winslow Plumber

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    450
    Location:
    Hawaii
    horizontal wet venting is not allowed under the UPC?
  12. Tom Sawyer

    Tom Sawyer In the Trades

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    It is allowed but a major fixture like the toilet can't drain past the outlet for a minor fixture like a sink or tub. Many plumbers think that doing so will cause problems with the operation of the minor fixtures drain with the possibility of pulling the fixture trap but, properly installed the engineering proves that there is more than enough air space above the waste in the lateral line to compensate for any passage of water. The IPC used to only allow wet venting provided the wet arm of the vent being 2" or larger but again, testing has shown that a single 1-1/2" pipe is more than large enough to properly vent two entire bath groups if properly installed. For many years I fought the IPC code too. Then I went to college and got a masters in plumbing engineering and that was a real eye opener. Many of the codes across the country are still hung up on technology and materials that are a hundred years old. We get set in our ways and many times our ways were our masters ways. When you ask why they say "we have always done it like that" I would estimate that I can walk into most houses that are in the rough plumbing stage and show the plumber on the job how he could have saved a whole lot of fittings, pipe and labor by changing his methods and materials.
  13. hj

    hj Moderator & Master Plumber Staff Member

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    a "cross tee" is not allowed, nor is a "double combo", for the two lavatories. It has to be a "back to back fixture fitting", and even then good practice would be to install a cleanout in the line below it. I didn't think the IPC did any testing. Their normal procedure would be if someone wanted to save some money he asked if the "easier way" could be done and it was approved then added to their "code", which was one reason their contractors rejected the agreement to merge with the UPC, since it would not be done that way afterwards.
  14. Tom Sawyer

    Tom Sawyer In the Trades

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    Neither of the code governing bodies actually do any testing. What they do is take their recommendations from plumbing engineers. Numbers dont lie. The volume of water flushed by todays code standards is less than half of what older toilets used to flush and yes indeed, you run 5 to 6 gallons of water past a tee outlet and it can cause "suction" to occur on that branch. However we are all pretty much flushing 1.6 and the volume there is nowhere near enough to cause a vacuum. In a properly designed wet vent system there will never be a time when any one branch has a water volume that fills a horizontal to more than 2/3 of its interior volume. IOW there will always be 1/3 of the space over the top of the waste being drained. Very few states still use the UPC. Partly for political reasons (money) but mostly because the code is outdated and cumbersome. For instance, and again because toilets dont flush 6 gallons anymore, there is no need for a vent to be within the percribed distances under the UPC. The IPC only requires a vent through the roof, somewhere in the structure. ( distance is unlimited ) and it makes sense because toilets don't need a vent as they are a full siphoning fixture. The vent coming from the fixture itself. As for back to back fixtures, the IPC does require a back to back drainage fitting for blow out fixtures. Standard flush toilets can use a combo or a double sanitary tee as can back to back lavs's ect. The standard reasoning from plumbers is that they can't snake the drain which is an excuse for not having the proper equipment.
  15. Terry

    Terry Administrator Staff Member

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    I'm going by field results.
    On a double fixture fitting for instance, flush a modern toilet with 3" flush valve will force water out of the opposing bowl.
    Running a modern toilet with 3" flush valve will affect the next toilet when flushed in a straight line.

    The old toilets flushed so slowly that it hardly mattered what you did.

    In Seattle, they make you bring the toilets in downstream of the other fixtures so that doesn't happen.
  16. Tom Sawyer

    Tom Sawyer In the Trades

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    I have honestly never seen that happen
  17. Terry

    Terry Administrator Staff Member

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    Last edited: Oct 25, 2013
  18. Tom Sawyer

    Tom Sawyer In the Trades

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    Interesting. I have the facilities here so perhaps we will mock a couple up and see what happens.
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