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Thread: Add a level, plumbing master bath

  1. #1
    DIY Junior Member brewdesign's Avatar
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    Default Add a level, plumbing master bath

    Here's the scenario. The house is a 2 bedroom 1 bath ranch with a massive add-a-level additon. The addition extends out the back (kitchen) on the main floor and the second story covers the entire main floor. The completed house nealy triples the house size. The new upstairs contains 3 bedrooms. A full bath is between two bedrooms. A master suite includes a master bath with 2 sinks, a drop in whirlpool tub, toilet and shower. The pictures and questions pertain to this bath group. A laundry group is present on the upper floor also.

    The original plumbing includes a 3" sewer main and 3" wet vent stack serving the main floor bath. This stack is not being used for 2nd story waste but rather a wye connection is present in the basement which connects the new soil stack to the existing one under the lowest main floor bath group connection via a wye. The existing wet vent stack will run up through the upper floor then connect to all other vents in the attic before exiting the roof.

    The wyes shown in the pictures accepting long bend 90s are for the master sinks (left most) and the laundry tub and floor dain (right most). Now for question #1. Is it acceptable to enter the tub drain through a reducing bushing in the straight end of the combo wye? Iwas concerned whether this causes solid waste buildup where the 1.5" line enters the straight inlet at the 3" combo wye. Question #2, can the upstream 2" toilet vent serve as the tub vent or will i need to install an additional 1.5" vent off a san tee on the tub trap waste arm before it enters the wye?

    Question #3, is there a preferred order of connecting the toilet, shower and toilet vent to the 3" waste line that runs into the afforementioned combo wye? Currently the order will be toilet at end then down the closet bend 2 feet where a reducing wye connetcts the 2" toilet vent (raising 45+ degrees then vertical to attic), then a flat wye receiving the shower waste and finally (providing no additional vent is needed) connection to the curved end of the combo wye.

    Other notes: there is adequate slope on the waste lines with some notching of the bottom of the floor joists, not exceeding 1/6 depth. The add a level is constructed so that there is a 5" chase between the bottom of the new upper floor joists and the finished main floor ceilings (1.5 separator plate plus existing 3.5 ceiling joists). The combo wye is not glued yet.

    Alternately I can send the waste line closer to the wall and insert a reducing wye and long bend 90 in place of the combo if that is a cleaner way to plumb it.

    Thanks in advance.
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    Last edited by brewdesign; 12-10-2012 at 05:40 PM. Reason: edit details, consolidate posts

  2. #2
    DIY Junior Member brewdesign's Avatar
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    Since there aren't replies does this mean i haven't done anything horribly wrong?
    Last edited by brewdesign; 12-10-2012 at 05:44 PM.

  3. #3
    DIY Junior Member brewdesign's Avatar
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    Default Wet vent stack diameter reduction

    The existing 3" wet vent stack serving one main floor bathroom group needs to run up an additional story (new 2nd story addition). For easier routing, is there a reason why the stack can't be reduced to 2" above the upper most waste inlet as long as the total vent area of the entire system meets or exceeds the original stack diameter? This seems to be an uncommon arrangement.

  4. #4
    Moderator & Master Plumber hj's Avatar
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    As long as you do not confuse diameter and area of the pipes through the roof, AND you city does not require at least one "full size vent" through the roof, assuming this is the only "large" one.
    Licensed residential and commercial plumber

  5. #5
    DIY Junior Member brewdesign's Avatar
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    Thank you HJ. The roof vent is 3". There will be mulitple vents converging in the attic to this one 3" roof penetration and they will exceed 7 square inches in area.

    Also, I posted additional questions in another post here:

    You just answered one of the questions I posted. I don't see a way to remove that post so that it can be re-posted in a more appropriate forum and I don't want to clutter things up with multiple postings. Suggestions?

  6. #6
    Moderator & Master Plumber hj's Avatar
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    One problem you will have, since you are adding 3 toilets is that the main line will have to increase to 4" where the "fourth" toilet connects. All the rest of the questions become convoluted and really need someone there to layout the plumbing, preferably a licensed plumber to do the work also. It is rather extensive for a DIY job over the Internet. You do not specify the depth of the floor joists, but I don't think I would be comfortable about "notching 1/6 of the way through them on the bottom, since that area is under tension.
    Last edited by hj; 12-12-2012 at 03:54 PM.
    Licensed residential and commercial plumber

  7. #7
    DIY Junior Member brewdesign's Avatar
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    Let me try to answer the points you raised, regarding the floor joists, they are significantly over sized with 2x12 @ 16" OC spanning only 12'. I oversized from 2x10 because I knew there would be drilling and notching (not to exceed code requirements). I agree that things are convoluted due to the nature of the project and if this were new construction, the plumbing layout would have been prioritized in the design and plans. I created the plans and built the addition and no matter how careful I though I was with layout I find things I would have done differently. That being said, this project is self funded and I have made significant compromises in labor budjet to be able to complete the project. Nothing has been subcontracted. If I could have, plumbing certainly would have been subcontracted. If inspection fails, I'll re-work it until it passes. Unfortuate but that's how it goes.

    Now to the "big" issue you raised --building drain size. A few years back I looked into this and thought I could manage by DFU load with 4 toilets on a 3" line. I'm looking at table 3004.1 for DFU and 3005.4.1 for maximum fixture units on the stacks and building drain. I essentially have 3 stacks. Stack #1 (5 DFU) is existing and serves the main floor bathroom, used for nothing else. Stack #2 (7 DFU) is the new stack in the picutres and serves the upper floor master bath. Stack #2 joins Stack #1 before it tuns horizontal in the building drain. A wye is present in the building drain that picks up stack #3 (9 DFU). So at this point the building drain is carrying 21 DFU on the way out of the house. Before it exits, however, the building drain picks up one basement 3/4 bath (5 DFU) and for about 3 feet carries 26 DFU before it dropps into a 6" main exiting the house.

    With that being said, 3004.1 lists 12 DFU as a combined 4-bath rating. Combined with the other units for the kitchen and laundry group, this totals 16 DFU using that method. 3005.4.2 lists 36 DFU on a 3" line at 1/8" per foot slope.

    BTW, I'm currently looking at 2006 Michigan Residential Code. I'll have to find the current code book as I don't have it handy but I didn't think anything changed from 2006.

    EDIT: I see this is IPC vs UPC. Unless things recently changed, Michigan is under IPC.
    Last edited by brewdesign; 12-17-2012 at 05:47 AM.

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