Basement Bathroom Addition

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by dekohman, Oct 28, 2004.

  1. dekohman

    dekohman New Member

    Oct 28, 2004
    Minneapolis, Minnesota goes! I've decided to add a bathroom (toilet, shower, sink) to the basement of my 1930's vintage home. The addition will be adjacent to where the sewer pipe drops into the foundation and right above the room there are vents that I can tie into. I've done some plumbing...but this job presents some new challenges for me, so before I launch into it, I'd appreciate any advice you can share! Here are my questions:

    1.) I have to open the basement floor to reach the sewer pipe; what's the best way to open up the floor if I want to do it myself?
    2.) The sewer pipe is cast iron...I want to put PVC in for the drains. How do I cut the cast iron and how do I join the PVC to the cast iron?
    3.) I presume it's acceptable to put PVC in the basement floor...covering it with cement when the plumbing work is done...any comments or other suggestions?
    4.) The shower basin will need a drain trap under it. The basin will sit just a few inches off of the floor though, so I guess that piece would actually be buried under the cement. Am I missing something there?
    5.) The bathroom is just 7X8 so all of these fixtures are next to each other. If I have one vent (off of the sink) is that sufficient to handle the other two fixtures...or do I need to vent the shower separately? The toilet drain will flow straight to the sewer pipe and the shower and sink drains will connect on each side of the new PVC sewer pipe, but all of these pipes will be fairly short; probably 5' or less.

    Thanks for your answers...looking forward to get ripping!

  2. LonnythePlumber

    LonnythePlumber Plumber, Contractor, Attorney

    Sep 6, 2004
    Plumber, Contractor, Attorney
    Wichita, Kansas
    To Work

    1. Breaking concrete. The concern here is not to crack your basement floor. You can use a saw or drill holes and then jackhammer. I use a concrete service when I can. You can save money on hauling away the old concrete if you wish but you won't have energy for something else that day.
    2. You can cut your cast iron with rented snap cutters, sawsall or grinder. Attach with a shield coupling like a no hub.
    4. The shower drain has to be exactly correct. Run your line over into the proximate location and build a one foot box in the expected area of the drain. This allows you to set the trap after the walls are built and you know where the receptor is going to be located. Being off 1/4" means you'll leak.
    5. You will probably drain your lavatories into the toilet vent. It would be better to have another vent for your shower but it is not required in all areas.
    You may also want to consider a back water valve. This is a swinging check valve that would serve the basement drains. They are now being required in our codes and they help (aren't perfect) slow sewer backups. You may also want to consider an exhaust fan if you haven't.
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  4. Deb

    Deb Plumber

    Sep 5, 2004

    You cannot do what you are proposing. I would recommend that you hire a plumber to at least lay this out for you. Plumbing under concrete HAS to be correct. Every fixture must be vented--it may be possible for 2 or more fixtures to use the same vent, however. This will depend on the layout of the basement and the code you are under. The toilet cannot run directly to the stack (it must be vented) and you cannot connect any other fixtures to the line between the toilet and its vent (which you have made no provision for). The shower will also need to be vented and trapped correctly. I generally run a horizontal trap arm to the approx location of the trap and box a 1' square out of the concrete to install the p-trap (when you install the shower). This also has to be vented correctly.
    You are going to have to take out way more concrete than just enough to expose the main (make sure that your main is deep enough to install the fittings you are going to need and still have grade). The toilet and shower lines need to be under the concrete, you will have your vent take-offs, and the connections to the main line.
    This is a really tough first plumbing project that requires some knowledge of plumbing and I believe that it may entail way more than you have imagined. Make sure that regardless of everything else that this is permitted and inspected.
    The Pipewench
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