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  • 1.  Sewer Lateral Configurations - P-Traps & Vent?

    Posted 04-02-2019 04:27 PM
    Edited by Tirza Austin 04-02-2019 04:26 PM
    Hi everyone,

    First post on ASCE Collaborate.  I don't see too much info regarding sewer systems, specifically lateral connections.  I'm an engineer at San Francisco conducting research for collection system lateral configurations. As a very brief background, San Francisco is predominantly a combined sewer system where stormwater and wastewater are collected in the same set of pipes. Properties in San Francisco are required to have a building vent / p-trap located within 2' from the curb line, on the sidewalk. The lateral is further delineated by the curb line to identify an upper and lower portion, both of which identifies various responsibilities of the property owner.

    I am researching how other cities have their laterals configured and seeking opinions to some very broad questions:
    1. How are other cities' lateral configurations?
    2. Is the building vent / p-trap configuration pretty atypical?
    3. Is there any concern of odors / gases / nuisances coming from the public sewer main into the property through a lateral without a trap?
    4. How are laterals typically accessed for inspection? Through cleanouts?
    5. Are laterals typically vented by a cleanout or is it sealed?

    Any feedback is appreciated.

    Thanks in advance,


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    Michael Tran P.E., M.ASCE
    San Francisco Public Utilities Commission
    San Francisco CA
    (415)695-7372
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  • 2.  RE: Sewer Lateral Configurations - P-Traps & Vent?

    Posted 04-04-2019 11:20 AM
    Edited by Tirza Austin 04-04-2019 11:19 AM
    Michael,
    I can only speak from my experience (others can other experiences).
    You are correct there is little information regarding sewer lateral connections out there at this time, hopefully that will begin to change.
    It is my opinion that one of the reasons we don't see much on laterals is it is generally considered to covered under building codes for plumbing and sewers.
    Below I've attempted to provide a brief answer for your questions.

    1.  How are other cities' lateral configurations?  I will say that is a loaded question, the cities that I've had a chance to work on sewer issues have standard details, but that being said, each site can have its own uniqueness.  In downtown areas I've seen the same type of configuration as you describe and other times we've found the clean out inside the building, in rural areas most have cleanouts next to the homes.  In one case where laterals were specifically addressed in a consent decree (Knoxville Utilities Board (KUB) in Knoxville, TN decided to put new laterals (with a "T" wye) in at either the back of the right of way or easement, this allowed them to inspect both the lower and upper portion of the lateral using a push camera.  The places we have address laterals (different places address them differently) are:  Knoxville, TN; Baton Rouge, LA; Gwinnett County, GA; and Salt Lake City, Utah to name a few.

    2.  Is the building vent/p-trap configuration pretty atypical?  My experience is yes.

    3.  Is there any concern of odors/gases/nuisances coming from the public sewer main into the property through a lateral without a trap?  Yes, I would be concerned of this possibility.  Also have seen issues where odors/gases/nuisances be an issue where P-traps had been installed where there was not liquid within the P-trap (it had evaporated)

    4.  How are laterals typically accessed for inspection?  Through cleanouts?  I my experience we have used the lateral launch cameras from the sewer mainline to inspect laterals as well as push cameras from cameras (suggest both types of these cameras be self leveling), note we did not allow these cameras to be used under any of the buildings.  At one time Montgomery, AL had a lateral program and they inspected using smoke testing.  Also (sorry I can't remember exactly who) one of the counties surrounding Kansas City, Missouri inspected laterals inside buildings.

    5.  Are laterals typically vented by a cleanout or is it sealed?  In my experience it should not be vented by a cleanout as the cleanouts are normally at ground level, the goal is to keep things out of the sewer that don't belong.

    Well I've taken up enough of your time and I hope this helps a little, if nothing else hopefully help start the conversation.
    Good luck with your research and I would be glad to discuss with you via a phone conversation anytime. 

    Have a great day!


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    C Douglas Jenkins, P.E., M.ASCE
    OBG
    865.382.2948
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    Original Message


  • 3.  RE: Sewer Lateral Configurations - P-Traps & Vent?

    Posted 04-05-2019 08:46 AM
    Edited by Tirza Austin 04-05-2019 08:46 AM
    I have never heard of p-traps on the service lines. Nor any odor problems for that reason. P-traps at the P/L seems to be just constructing an unnecessary trouble spot.
    (P-traps are, of course, required on all fixtures inside buildings by the plumbing codes).
    Service lines  are required to have a double clean-out by the building and otherwise as required by the UPC for longer lines crossing a property. Service lines are capped; not vented.

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    Hans H. Coucheron-Aamot
    [Retired]
    Albuquerque NM
    (505) 897-2554
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    Original Message


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