Trap-to-stack distance - how big a fuss to make?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by paulc, Dec 14, 2007.

  1. paulc

    paulc New Member

    Messages:
    4
    Hi all

    I'm having a GC do a fairly large project on my house, and the plumbing sub has done pretty good work to date. Having done a lot of my own plumbing in the past I'm pretty familiar with the code.

    At the moment they are roughing in a shower drain. I can't tell 100% that they are done, but it appears that if they are they're planning on running the 2" drain about 6' to the stack with no intermediate vent. In addition the path from the trap to the stack has a 90 degree turn (done with a sweep 90).

    Am I right to assume that they need to put in a branch vent for the shower before 5', and before the 90 degree turn? I want to make sure everything is done properly, but more importantly I want it to work without issue.

    Normally I'd just talk to them directly but their English is not the best and I want to make sure of the facts before I talk to the GC.

    Thanks

    Paul
  2. BAPlumber

    BAPlumber Plumber

    Messages:
    227
    Location:
    Vashon, Washington
    I'd talk to the GC. The plumbers work for him. it's your house, if you have questions, ask. Is this permited, and will it be inspected?
  3. paulc

    paulc New Member

    Messages:
    4
    Good point.

    If it's going to be flagged in the inspection I'm better bringing it to their attention now while the work is still fresh rather than waiting. If the GC says it's no issue and it passes inspection ok.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,286
    Location:
    Cave Creek, Arizona
    vent

    There is often a little distance between what the code approves and what will work without causing a problem. But if the inspector approves it then you have nothing to worry about.
  5. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    Under the IPC the 90 laying horizontal is OK, you can not have the bottom of the pipe at the fixture trap higher than the top of the pipe at the vent, if that makes any sense. The code says weir not above vent opening. The elevation of the pipe is important when you run the max distance allowed. Under the IRC a 2" pipe can go 8' the UPC is less something like 5'. The rules are different for toilets.
    Last edited: Dec 15, 2007
  6. yes, the weir and the vent opening - think of it as the top and bottom edges of the inside walls of the pipe -- so if you position the pipe to have a slightly gentler slope than 1/4" per foot fall, it can go a longer distance while still remaining within that top-bottom constraint. And a 1/5" per foot fall is still enough for water to slide through and out of a pipe. F.Y.I.

    the codes that shrink the distances are adding in a margin of safety.

    david
  7. smellslike$tome

    smellslike$tome Plumbing Company Owner

    Messages:
    92
    Location:
    Birmingham, Alabama
    I see plumbing systems all the time that somehow passed inspection but are immediately identifiable as installations that were not done by competent, certified plumbers. Generally the further you go in these systems the worse they get. Ultimately I would not rely upon what the GC tells me but I would want to see the certification documents of the lead plumber who is on site and in charge of your plumbing installation. It is very disturbing that they can't speak english. If they can't speak english then it is not unreasonable to think that neither can they read english. If they can't read english then what is the likelihood that they could pass any sort of plumbing examination required for certification in most places.

    Having said all that, the IPC allows 6' for a 2" line with a 2" trap regardless of horizontal offsets. I don't know what the UPC allows and don't know which you are governed by.
  8. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    2006 IPC Table 906.1 maximum distance of fixture trap from vent: size of trap in inches 2", 1/4" per foot slope, distance from trap 8 feet. That's a fixture vent common vents have a lot of different rules depending on how they are connected determines which fixture is being vented. There are a lot of rules on venting depending on the situation.

    I've read that 6' thing in a lot of posts and don't know where it comes from, there is a chart in the IPC and UPC. The UPC is harder on venting all around. 6' must be some generic guide people use.

    It all has to do with the verticle slope and the weir of the pipe can not be higher than the vent inlet. The weir is where the water starts to flow out of the trap.
    Last edited: Dec 15, 2007
  9. smellslike$tome

    smellslike$tome Plumbing Company Owner

    Messages:
    92
    Location:
    Birmingham, Alabama
    I have to confess that I'm working from the 2003 IPC. Most municipalities around here are slow to take up the most recent code. Before it was the IPC we used the Southern Building Code Congress. In 2000 and earlier versions the distance was 8' but I think it was for 2" waste with 1 1/2" trap and 6' for 2" waste and 2" trap. I have never understood why. Anyway the 2003 has it at 6' for 2" waste regardless of trap size. If they have gone back to 8' for 2006 then that is even better.
  10. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    I don't know about better, it seems the IPC and UPC are getting farther apart, so much for a single uniform code, maybe the talks are not going so well.

    I have the 2003 IRC for one and two family dwellings book and it has the same chart as the 2006 IPC book.
    Last edited: Dec 15, 2007
  11. smellslike$tome

    smellslike$tome Plumbing Company Owner

    Messages:
    92
    Location:
    Birmingham, Alabama
    It doesn't really matter to me. As long as I know what the rules are I am happy to play by them. I guess that is why I haven't really delved into the 2006 IPC yet because none of the municipalities around here have signed onto it. We have some that are using 2003, some 2000, and at least one if you can believe it that is still stuck in 1994. It would be nice if everyone would get on the same page, whatever page that might be and if they announce one day that we're tossing the IPC in favor of the UPC, well that will be ok too. I'll buy whatever UPC version they want to use and learn it.
  12. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    I never understood why they worry about distance, yet not about bends on anything except cleanouts. You would think a bend would matter in a venting situation, it does on direct vents for furnaces and hot water tanks as well as dryer vents.

    Does it matter just not enough to worry about?
  13. Herk

    Herk Plumber

    Messages:
    547
    Location:
    S.E. Idaho
    A 90 degree bend is also legal in a trap arm under the UPC.

    I remember older codes that allowed further distances from the vent as well. So, in regards to it working, I doubt you'd know the difference. For one thing, when taking a shower, the pipe is not likely to ever fill with water unless it's plugged.

    Further, these distances were probably figured before the government began mandating lower gallon usage for shower heads.
  14. smellslike$tome

    smellslike$tome Plumbing Company Owner

    Messages:
    92
    Location:
    Birmingham, Alabama
    Bends in exhaust piping have a bearing on the formation of condensation and is probably why they are a bigger deal since condensation will shorten the life and affect the efficiency of water heaters and furnaces. If you have water in a plumbing vent it affects nothing unless their is actually a water seal somewhere in the vent.
  15. smellslike$tome

    smellslike$tome Plumbing Company Owner

    Messages:
    92
    Location:
    Birmingham, Alabama
    I bet you are right although I never really thought about it.
  16. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    Is it a stack or is the piping above the vent. Depending on the code in use the trap to vent distance may varry. According to the UPC a 2" trap arm can be 5 ft in lenth and contain up to 90 deg offset.
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