(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 6 of 6

Thread: Basement rough-in

  1. #1

    Default Basement rough-in

    My home is 3 years old [2 story plus above ground basement - called terrace level around here] that has rough-in plumbing for a bath in the lower level [floor is concrete]. I have hired a local plumber to help me finish the bath.

    We have three capped PVC pipes sticking up out of the concrete floor -- one for the toilet, one for the shower, and one for the lavatory. We are also tapping into the drain system to add a utility sink and a bar sink in different rooms.

    My plumber said it's a simple matter of cutting off or extending the respective drain pipes and installing the fixtures -- then teeing-off the existing hot and cold supply lines to finish the job.

    When I asked him about venting, he informed me that this was all taken care of during the original rough-in plumbing. He pointed to the main drain stack which services the higher floors and said that it extends out through the roof and provides all the venting necessary. This was not a satisfactory answer and I pressed him further, but he maintained his position.

    The shower drain has a buried p-trap under the slab, the toilet has its own p-trap, and each of the three sinks will have a p-trap. The basement has stud walls only, so nothing is hidden.

    Question 1: In new home construction, when a home is "plumbed for a basement bath", is the required venting somehow "taken care of" in ways that are not obvious -- when you only have stud walls, with no drywall installed?

    Question 2: Isn't it true that each of the fixtures must have a separate vent just beyond its trap to balance the pressure and prevent a vacuum which could suck the water out of the trap? Isn't this the purpose of a revent?

    Thanks, I really need an education on the venting issue.


  2. #2
    Plumber RioHyde's Avatar
    Join Date
    Sep 2004
    Cincinnati, Ohio


    When a basement bath rough in is done here, all the drains that are plumbed are vented. Here it is usually with a wet vent. You say you're adding a utility and a bar sink. Neither of these fixtures are already vented as neither of them were ever plumbed in the first place. Each fixture must be vented according to whatever code is applicable in your area. In addition there are quite a few different venting systems that are used. If the bar sink and the utility sink are back to back, a common vent might be used. If not, they will have to be individually vented then tied into the vent that has already been run for your basement bath rough in. The main drain stack CANNOT be used for a vent. Fixtures on the upper floors drain through this thus it is a drainage stack not a vent stack. Flush toilets, run sinks and tubs and listen. If you hear water running down the pipe, that IS NOT a vent stack.

  3. #3

    Default Thanks RioHyde

    How do I recognize a wet vent?

    Standing in my basement looking up, I see a number of pipes from all directions feeding into one major vertical stack which disappears into the concrete floor and goes horizontal out the side of the house. The bath drains [for the basement rough-in] connect into this horizontal section before it leaves the house.

    I don't see any other vertical PVC in the basement space other than this main stack.

  4. #4
    Plumber RioHyde's Avatar
    Join Date
    Sep 2004
    Cincinnati, Ohio


    Do you see an 1-1/2" or 2" vertical line with a capped tee in it for your lavatory? Out of the top of that tee is a vent. I think Terry has a drawing of a wet vent in another post, not sure. The thing is, you need to identify the vent for this bathroom group. Where you would tie into this vent is the "dry" vent even if it is from a wet vented group. Check with your local code official's office, but I'm relatively sure you'll be about to tie a utility sink and a bar sink vent into what you already have there.

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Bothell, Washington
    Blog Entries

    Default Plumbing waste and vents for more than one story

    A two story waste and vent job can look like this.
    Vents are tied in 6" above the flood level of the fixtures served.
    You will note that the lower floor vents tie in at 6" above the next floors plumbing fixtures's flood level.
    No waste lines are used as vents.
    It would defeat the purpose of the vents.
    You really only have one chance to have it right.
    I hear so many stories of bad plumbing behind walls, making it difficult to repair and make right.
    Notice that the vent for the 1st floor tub ties in on the second floor at 42".

    The waste line for the toilet is the only one that does not have a p-trap. The trap is internal to the toilet.
    If you look at the side of a toilet, you will see the curve that goes first up, and then bends down is the trap. The high point of the bend, becomes the level of water in the bowl.

    If the vent can't go up, because you are on an island, then some codes allow the vent to go back below the floor. This is done by tying the vent back into the waste line using drainage fittings.

    However, before it ties back in, a "foot vent" must be added.
    A foot vent will run from the loop until it finds a vertical area so it too can reach for the sky. Where the foot vent turns vertical, you will have an accessible clean out.
    The foot vent won't do much good if it becomes blocked. A clean out will help if that ever happens.
    All fittings below are to be waste fittings, things like wye's on the horizontal and proper bends.
    Last edited by Terry; 09-08-2005 at 11:17 AM.

  6. #6

    Default For Terry

    My county building department tells me the solution for my problem is to install a "Studor Vent" at the lavatory drain connection.

    Almost every new house built here is a 2-story w/basement which has a stubbed in bath. The studor vent is used unless the builder has provided a capped-off vent line for the space.

    Starting this year, they have made the capped-off vent line a requirement for new home construction.

    This is Forsyth county, Georgia, north of Atlanta.


Similar Threads

  1. Basement rough in - does this look OK?
    By export! in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 6
    Last Post: 07-22-2011, 11:44 AM
  2. Basement Rough In
    By jimdeprado in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 05-20-2008, 07:56 PM
  3. basement tub rough in
    By cruiser in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 7
    Last Post: 08-15-2007, 07:44 PM
  4. Basement Rough-In
    By srk in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 5
    Last Post: 05-18-2005, 05:51 AM
  5. New Basement Rough-in
    By macheske in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 14
    Last Post: 04-17-2005, 03:45 AM


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts