Replacing Cast Iron Sewer Lines In Crawl Space

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DanMcD, Jun 19, 2005.

  1. DanMcD

    DanMcD Member

    Jun 19, 2005
    Dayton, OH
    Terry and Forum Friends,

    I would like to get some advice on best plumbing practices regarding replacement of my cast main sewer pipelines with PVC piping. My plumbing is in a crawl space, so I have some concerns about possible leaks years down the road. My concern is about the pipes that carry the wastewater and not so much on the vent pipes (at least I think these are not an area to be concerned about). I would like to know:

    1) Would it not be best if a plumber replaced my cast pipe with new cast pipe versus using PVC?

    2) What is the best way to connect new PVC to the old cast iron main sewer line pipes? I think they are 4 or 5 inches in diameter and I’m concerned about leaks in the crawl space that I may never see. Thus, I am concerned about the use of any rubber connectors: their life expectancy and reliability. Also, I am concerned about expansion that might cause the connection to come apart. My longest main sewer line is about 24 feet before it goes outside of the foundation wall. Specifically, would it be best to:

    a) Bring the PVC pipe all the way outside through my foundation wall and avoid any inside connection.

    b) Use some type of non-rubber connector to make connections that must be done. For example my 2-inch cast iron drainpipe that is for the laundry room must be connected somehow. The reason is: It is 20 feet long with half in the crawl space, but the other half in the inside of the house in the laundry room and buried under a concrete slab. Thus, the last 10 feet in the crawl space can be replaced with PVC, but it needs to be connected.

    3) What is the best practice to hang the new PVC pipes and support them to the floor? My cast pipes are on the ground supported by 3 bricks every 5 feet or so. I hope there are quality pipe hangers that plumber’s use. Using wraps of metal tape does not sound good to me.

    4) With 20 feet of main PVC drain pipe, what is the best practice to deal with any expansion of the PVC due to temperature changes.

    5) Should I have an access drain installed outside of the foundation wall.

    I know these are a lot of questions, but I'm hoping some of you have first hand experience in these matters.

    Dan McD
  2. Dunbar Plumbing

    Dunbar Plumbing Master Plumber

    Apr 18, 2005
    Service Plumber, Outdoor Temperature Relief Owner
    Northern Kentucky/Greater Cincinnati Area
    1. You can use either but PVC has a better reliability
    2. Mission no-hub couplings; rubber couplings with SS bands and shield.
    3. Support piping every 4 to 5 feet.
    4. Expansion shouldn't be an issue as long as you do not stress the piping into place.
    5. Have a cleanout where you have the best way to set a drain cleaning machine to operate with little effort.
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