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Thread: Can I do this? Double waste system ?

  1. #1
    DIY Junior Member petros151's Avatar
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    Default Can I do this? Double waste system ?

    I posted this in the UPC section but I think it should have gone here. sorry for the dup.

    I have a potential problem. I have an old house there was originally no plumbing (1900) and an out house. At some point they put a full bath in upstairs and it is
    plumbed in the floor and vented from the bathroom (2nd floor) up to the roof.

    Then at some point they put in a kitchen sink on floor 1 and a washer drain neither of which is vented. They work fine and the S traps seem to be keeping full no aspiration etc...

    Now I need to put the kitchen sink (1st floor) about 20' from it's current location (moving the kitchen to another room) and also set up a laundry room with half bath on the first floor.

    The 2nd floor drains down a verticle stack and into a horizontal run that goes out the house.

    If I mess with that horizontal run in order to send the new fixtures into it I will loose my grandad clause and most likely have to tear out the cast iron stack from the 2nd floor and replace the cast horizontal run with PVC and then hook up the new stuff. Could be expensive taking out the 2nd floor stuff. It works great I hate to mess with it.

    One way to solve the problem would be to not touch my existing cast iron plumbing waste stack and use a parallel system to serve the
    new kitchen sink and new 1/2 bath install and a laundry room W/D set up. I was hoping I might be able to run all this using pvc and a new vent system and let it drain into the sewer via a Y where the cast goes out the house. OR I could possibly dig outside the house and tie it in right after it
    exits.

    So far 5 plumbers I have called are too bust working on furnaces to come over before December. I don't want to call the inspector yet until I have some idea of what I can "get away with"

    I'm in PA

    has anyone ever heard of a split system like that?

    thanks

  2. #2
    Moderator & Master Plumber hj's Avatar
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    It is NOT a "split system". MANY houses have multiple vertical stacks when the plumbing fixtures are separated. "S" traps do not normally "aspirate", but they can when water rushes past their connection. However, EVERY "S" trap siphons, regardless of whether you think it does or not.
    Licensed residential and commercial plumber

  3. #3
    DIY Junior Member petros151's Avatar
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    Default correction on can I do this?

    thanks for the info . I need to correct my description

    I would not have multiple vertical stacks but 2 horizontal runs. Here is a diagram what is blue is new what is brown is old Cast iron. All the new stuff
    is going to have to drain into a horizontal run just below he 1st floor in the basement. There is no vertical run involved. So I will have two horizontal
    (sloped of course) runs that could Y together just before they exit the house. I am trying to work out a way to not touch the brown stuff old work so as to not
    disturb anything and then just create a whole nother set of pipes that are the blue. I did not include any vent just to simplify but it would be vented out the roof
    for the blue system.

    So is this something that can work?

    Thanks
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  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    By code, every trap should be vented. So, all of the new stuff should have a proper vent. You can keep from making a new penetration through the roof if you wish, but you can't connect into that until it is at least 6" above the highest flood plane, or 42", whichever is higher (probably easiest in the attic).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Moderator & Master Plumber hj's Avatar
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    YOu can have as many "horizontal systems" as you want, and they can either be parallel or at angles to each other, it makes no difference. BUT it SHOULD have, and may REQUIRE, at least one vertical vent pipe., depending on your code and HOW you arrange, and pipe, the fixtures.
    Licensed residential and commercial plumber

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