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Thread: Soil pipe depth requirement

  1. #1

    Default Soil pipe depth requirement

    Is there a depth requirement for a soil pipe that runs outside a building? Old house with an addition on the back and an exterior 3" vertical wasteline from the second floor. Some previous owner installed and uninspected half bath and ran the soil pipe (schedule 35 PVC) across part of the yard and tied into the base of the exterior verticle waste stack that goes into the basement. I want to enlarge the bathroom and also bring the plumbing work up to code. To maintain pitch I will only be about 10" below grade when I come thru the foundation wall of the addition. Is that deep enough?

    My other option is to go thru an 18" thick stone wall with a 3" line into the basement and install an ejector pump setup to get the waste up and over the basement area the would need to be crossed.
    Last edited by mreeves; 01-10-2006 at 05:44 AM.

  2. #2
    DIY Senior Member rshackleford's Avatar
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    does it freeze in your area. this would be one controlling factor on depth.
    rshackleford

  3. #3

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    Location is New Jersey. so yes it does freeze. Water supply lines need to be 36" below grade here.

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default depth

    In many cases, you do not have any control over the depth of the pipes, freeze area or not, because you cannot go lower than the pipe you are connecting to, less the required pitch by the time you get to the plumbing fixture location. I have installed sewer lines 3" below the ground because that is where it wound up by the time I installed the lateral run to the addition.

  5. #5
    Plumber Cass's Avatar
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    Most sewer lines never freeze no matter the depth as the air temps inside tend to be above 32F reguardless of the outside temps.

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    In the Trades Gary Swart's Avatar
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    Another reason not to worry about the freezing, a sewer line does not contain water except when something is draining, and the somewhat warm water is moving. It would have to be extremely cold before it would freeze moving water.

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    DIY Senior Member rshackleford's Avatar
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    we will sometimes get a week or two of twenty below weather and lots of things will freeze then. this is why i think about freezing a lot. if you get lots of snow cover and moderate temperatures freezing will probably not be as big of an issue.
    rshackleford

  8. #8

    Default

    Sounds good. Thank you all for your advice.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default freezing

    If the pipe is shallow, then the surrounding ground can be below freezing temperature. Moving water will freeze if it stays in contact with the cold long enough. (Ever seen a picture of a frozen waterfall, or river?) As long as the plumbing is working properly it will not freeze, but if a toilet or faucet is leaking then that small flow of water will freeze. It will be cumulative so as it freezes it will create a dam causing water to accumulate and freeze behind it and eventually fill the pipe with ice.

  10. #10
    DIY Senior Member rshackleford's Avatar
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    i would use some dow board to insulate above shallow lines.
    rshackleford

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default dow board

    Quote Originally Posted by rshackleford
    i would use some dow board to insulate above shallow lines.
    Save your money. It would not do a bit of good, and would not protect anything.

  12. #12
    DIY Senior Member rshackleford's Avatar
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    please explain to me why it would not help.
    rshackleford

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    Insulation slows the transmission of heat. A sewer pipe that does not have anything running through it basically has no heat in it to move. Anything that moves through it is only transitory, and wouldn't heat it up enough to make much difference with trying to slow its dispersal with insulation. So, you've got cold ground with an unheated pipe going through it, so what heat would the insulation slow? My unprofessional thoughts.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Plumber Cass's Avatar
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    Ground heat?

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    DIY Senior Member rshackleford's Avatar
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    the insulation would slow the loss of the heat from the earth to the atmosphere.

    i have been told that a 2" piece of dow board is equivlant to one foot of earth cover. i guess i could do the math, but does anyone else have thoughts on it.
    rshackleford

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