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Thread: Basement DWV

  1. #1
    DIY Junior Member UtahSpike's Avatar
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    Default Basement DWV

    I'm planning on finishing my basement and when building my house (1999) I had two full baths roughed in. Since then, I have decided to increase the size of one of the baths and add a small kitchen. So here are my questions:
    1. At the location of the original sink in one of the bathrooms (the one I wish to make larger) - I would like to change to a stackable washer/dryer. As the drain and vent are both 2" - would this be a problem?
    2. I would like to add two sinks in the expanded bath on one side of a wall and a kitchen sink/garbage disposal/dishwasher on the other side of the wall. I plan on using the proper size drain and vent (2" in this case.) Can I send this combo (4 d.f.u.) drain into the 2" vent for the nearby toilet? It would make that dry vent stack 'wet' for about 2 vertical feet then increase to a 3" drain at the toilet.
    I can find nothing in the code (2006 IRC) that would prevent me from doing this. I've checked and double checked the code for sizing, distances, everything seems to be code.
    However...I have read in this forum and on other web sites a couple of things that concern me.
    1. You cannot combine bath and kitchen DWV.
    2. The maximum traps on any one vent stack is 6 (including a max of 2 toilets.) These roughed in two full baths eventually combine into a 3" vent stack that is exclusive for the basement baths.
    If need be - I can cut and trench the basement slab and independantly drain the kitchen items - but I'd like to avoid that if at all possible.
    Thanks in advance for any advise you can give me!

  2. #2
    Homeowner geniescience's Avatar
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    Default not Code. Works like

    Quote Originally Posted by UtahSpike
    1. At the location of the original sink in one of the bathrooms (the one I wish to make larger) - I would like to change to a stackable washer/dryer. As the drain and vent are both 2" - would this be a problem? ....
    Code in your area calls for a 2" pipe, and what is installed is a 1.5" pipe, is that what you are saying? I'll just say that it used to be Code to have a 1.5" diameter drain for washing machines, and these drains still work today. Where I live it still is Code. I had a top-loading washer for 20 years on a 1.5" drain. Now I have a front-loading washer. My building has 50 more drains like this; it's a highrise condo building. I think people will tell you that a 2" drain handles the flow better, and doesn't risk overflowing. FYI a front loading washer uses much less water than a top loading washer.

    Also, regarding 1.5" or 2" drains, Code used to call for a 1.5" drain pipe for showers and now it calls for 2" drain pipe. Many people who install new showers onto old 1.5" pipe reduce the new shower drain to 1.5" instead of replacing the whole pipe and Tee. What a larger pipe does is carry more water and air, the air being necessary to make up the volume displaced by the moving water. Note that Code calls for a 1.5" drain pipe for a tub-shower. I think the rationale is that a blockage in that drain pipe is less critical there since the tub would hold the water that backed up.

    Best draw a sketch for your other, bigger, questions.

    david
    Last edited by geniescience; 03-01-2007 at 06:21 AM.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default bathroom

    A picture or drawing is necessary, because it is hard to follow the description and be exactly sure what you plan to do. In theory, there is no problem making the changes but how you would do it is what would make it right or not.

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    DIY Junior Member UtahSpike's Avatar
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    Default Here's a drawing

    I hope this blueprint helps. The lower (smaller) bath has all fixtures located exactly where they were roughed in. I want to change the upper (larger) bath in the following ways:
    1. Where you see a closet between the bath and toilet is currently roughed in for a single sink. In that closet I want to change to a stackable washer/dryer. The drain and vent are already roughed in 2". I don't think this would be a problem.
    2. I want to add a double vanity and kithen sink/garbage disposal/dishwasher (the ones at the top of the picture.) I want to use the vent for the toilet that is adjacent (below in the blueprint.) This vent is 2". Each toilet you see has its own 2" vent already roughed in.
    The vent for the added bathroom sinks and kitchen sinks can be 2" and can be located immediately behind them in the wall and be code for critical distances, size, etc. - I'm not worried about that.
    What I would like to know is can I drain the added fixtures (2 baths sinks @ 1 dfu each + kitchen sink/garbage disposal/dishwasher @ 2 dfu=4 dfu) down what was (as still would be) the vent for the toilet (2" vent.)
    As I mentioned earlier I have read on this forum and on other internet sites (but can't seem to find anything in the applicable local code - 2006 IRC) that:
    1. "Only four water closets or six-unit traps allowed on any vertical pipe or stack; and not exceed three water closets or six-unit traps on any horizontal branch or drain."
    2. You cannot combine kitchen and bath DWV on any single branch or stack.
    Any help would be graetly appreciated. Thanks!!!
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  5. #5
    Homeowner geniescience's Avatar
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    Default three answers

    One thing at a time.

    Washer: You have a 2" and you need a 2", and you have no problem, and you just wanted confirmation, is that the way I ought to read it? If yes, then your answer is "Yes, and you still need the standpipe and trap for a washer."

    Then, venting the wall between the vanity and the kitchen sink is Yes the right thing to do.
    Quote Originally Posted by UtahSpike
    .... add a double vanity and kithen sink/garbage disposal/dishwasher .... use the vent for the toilet that is adjacent .... The vent for the added bathroom sinks and kitchen sinks can be 2" and can be located immediately behind them in the wall ....
    Good so far. A new vent branching off from the toilet vent (at 42" above the floor or higher), going over to the kitchen + vanity wall.

    Then,
    Quote Originally Posted by UtahSpike
    .... What I would like to know is can I drain the added fixtures ... down what was (as still would be) the vent for the toilet (2" vent.)
    This is hard to understand. You have got to describe the drain. Once waste water flows into a vertical vent, the pipe is now a drain, not a vent. Where do your drains go? Apart from changing the word to "drain" you also have to know where all the drains go to.

    Then, how to connect to the toilet drain, with Wyes, can be described later.

    If you don't know where your drains go to, you need to look and find out.

    Then, about combining kitchen and bath DWV on any single branch or stack, I don't know.

    David
    p.s. after rereading, I think you may be hoping to connect the kitchen-vanity waster above the floor level into the toilet vent... Is this an accurate rewording of your question?
    Last edited by geniescience; 03-01-2007 at 09:29 AM.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default picture

    The drawing is a bit large, but now you have to insert the pipe locations and sizes so we can tell what is okay and what has to be changed.

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    DIY Junior Member UtahSpike's Avatar
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    Default Where the drains go

    David,
    You are very good at translating my post - thanks!
    1. Yes - I was just looking for confirmation on the washer. I got the confirmation - thanks!
    2. Yes - I am hoping to connect the kitchen vanity waster above the floor level into the toilet vent.
    3. The 2" vent for the toilet that I am hoping to connect into (and turn into a drain) is on the discharge side of the 3" toilet drain. This drain and the other 3" toilet drain (with its own 2" vent on the discharge side) wye into a 3" branch and then eventually wye into the main 4" drain.
    Can I do this? Would I be turning what was a 'dry stack' into a drain or 'wet stack'?
    So I guess it boils down to this - can you drain down a vent stack even if it is only for a couple of vertical feet?

  8. #8
    Homeowner geniescience's Avatar
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    Default draw drains in floor.

    No.
    Quote Originally Posted by UtahSpike
    ....
    2. Yes - I am hoping to connect the kitchen vanity waste above the floor level into the toilet vent.
    3. The 2" vent for the toilet that I am hoping to connect into (and turn into a drain) is on the discharge side of the 3" toilet drain. ....
    Draw a simple floor plan diagram showing the route taken by the 3" segments and the 4". Then you will get good advice. The new vent at the vanity-kitchen wall needs a new drain. That new drain needs to be connected to the existing drain setup. That connection is not easy to advise on unless you draw the geometry with a few lines.

    david
    Last edited by geniescience; 03-01-2007 at 12:04 PM.

  9. #9
    DIY Junior Member UtahSpike's Avatar
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    Default Floor Plan

    Sorry for the huge drawing again. FYI - off the drawing to the left is a floor drain in a utility room and the two unlabeled toilet vents are 2" each. Incidentally, each vent location has a cleanout.
    I'm presuming I'll have to cut and trench the concrete for a 2" drain with a 1/4" drop/foot into the main 4" line at a 45 degree angle?
    Anticipating questions about the added bathroom sinks and kitchen.
    1. The bathroom sinks will be separated by drawers so each sink will have to have it's own drain.
    2. The kitchen group on the other side of the wall will have a dishwasher discharging into a garbage disposal and I only have enough room for a single kitchen sink (in spite of what the drawing illustrates).
    As was addressed earlier, the venting for both these groups will not be a problem - I just need to know where in relation to the kitchen/bath sinks to place it.
    Thanks!
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  10. #10
    Commercial Plumber markts30's Avatar
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    Default

    I think your best bet would be to cut the slab and put a new branch on the 4" main - use a 4 X 2 " Combo and take new risers up to catch the 2 lavs and sink...
    Last edited by markts30; 03-01-2007 at 02:12 PM.

  11. #11
    Commercial Plumber markts30's Avatar
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    Default

    By combo I mean a fitting that is a combination wye and 1/8th bend - that would bring you off the main at a right angle and make your digging less and cutting less...
    It would also use less pipe and the layout is easier...
    The heavy rectangle is where I would cut (extend it to cover the last lav as well)
    I have drawn a quick lateral drawing too...
    Make sure if done this way the last riser comes up full size (2") for an end of line cleanout if required... (dimensions are not on the drawing...)
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  12. #12
    DIY Junior Member UtahSpike's Avatar
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    Default Almost there

    Thanks for the excellent render! Where in the additional DWV would I install the vent(s)? I would think to vent each of the 3 drains and joining those vents horizontally (with 1/4"/foot rise) running the same direction as the drain into the existing 2" vent. Correct?
    Would I need to provide a cleanout(s) anywhere in this design?
    Thanks!!!

  13. #13
    DIY Junior Member UtahSpike's Avatar
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    Default Cleanout

    Sorry...just re-read last post and saw the refence to the cleanout location...Thanks!

  14. #14
    Commercial Plumber markts30's Avatar
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    Default

    Yes - revent them in the wall at least 6" above the flood rim of the highest fixture

    Sorry for the delay - deleted the original dwg I did..
    Redid it to show some reventing...
    Name:  Basement revent1new.jpg
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    Name:  Basement revent2new.jpg
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    Option 2 allows you to tie into another vent without boring all the way back through the wall... You can do it above the ceiling if that is an available option...

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