Options for dealing with condensate and T&P in basement?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by dgeist, Jul 26, 2017.

  1. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    I'm tying into existing DWV to create a new basement bathroom group. Just a few feet away, I have a high-efficiency furnace and a condensing tankless WH. Both produce a decent amount of condensate an the later also has a T&P valve. Right now, all air-gap "drain" functions are into an open (non-sewage) sump w/quality submersible pump that goes up and to daylight if rainwater comes up too high under the basement slab or if I had a gallon or more of condensate/overflow from the appliances. I'm replacing the tile sump pit with a sealed unit for various reasons, radon and air leakage among them. I do still need to deal with the appliances needing to drain. Here are my options:

    - have the contractor add a floor drain behind the side wall of the bathroom next to the current sump location. Venting is a concern here since the only way it could get makeup air as they've proposed it is from a vertical 4" waste stack serving two bath groups and a kitchen above.

    - have the contractor make a purpose-built standpipe with a 3-4" opening 18" above the floor. Similar concerns to floor drain, but slightly less likely to ever back up and possibly "neater".

    - construct a trapped floor drain/pipe that drains into the sump basin concealed below the finished concrete. The trap would keep the basin water/airtight, but I would have a risk of depending on that sump pump to keep the system from overflowing if I ever had a REAL T&P emergency.

    The options seem like they each have risk/rewards, but I'm curious what folks have done in similar situations.

    Dan
     
  2. Stuff

    Stuff Well-Known Member

    Joined:
    Mar 7, 2013
    Location:
    Pennsylvania
    It is common to use a condensate pump to go to a laundry tub, sink tailpiece, or even outside. So the real issue is the T&P valve.

    How is the new bathroom going to be vented? Might be able to tie into that. Any other floor drains in the basement?

    Also a floor drain might need a trap primer.
     
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  4. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    The new bath group will have a common vent that goes upstairs into an existing wet wall and tying into the dry vent of the half bath there. I believe I COULD run a separate fixture vent up the other (currently non-wet) bathroom wall and tie it in. It'll just be some PVC fitting spaghetti.

    No other fixtures or openings of any kind presently in the basement other than a couple clean-outs. Only a 4" stack serving the areas above tied into another similar stack on the opposite end within the slab and leaving out to the city sewer.

    Trap priming should not be a big deal with the condensate from the water heater (if it's going to a trap). It drips pretty much constantly whenever hot water is being made. Water heater and furnace location are in the bottom right of the diagram, drains easily plumb-able to any indirect receptor in that area.

    Attached below is an isometric for the DWV system as proposed today. Sorry for the poor scan quality. I don't have a good electronic tool but do have isometric paper... The WC and tub are wet-vented by the 2" lav (and sink on opposite side of wall) drain, which itself is dry vented up and and to the existing dry vent in the level above.
    drain_isometric_for_g-force.jpg
     
    Last edited: Jul 27, 2017
  5. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    Here's a top view of the same system with my proposed location of the floor drain off the 3" horizontal bathroom branch. New PVC drains are in turquoise. PVC dry vents in yellow. Fixture placement shown by dotted blue outlines. Sweep bends to be used in horizontal waste, sanitary tees in vertical vents. A section of 3" drain between the left wall and the junction with the 4" drain has a clean out under the sink in the "kitchenette" and serves as as wet vent for the wc and tub. I also added an inline 3" backflow preventer to protect all the new fixtures. Do all the drain and waste paths/locations/sizes make sense?

    Dan

    basement bathroom dimensions closeup DWV v2_cropped.png
     
  6. Stuff

    Stuff Well-Known Member

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    Mar 7, 2013
    Location:
    Pennsylvania
    First you need a separate dry vent for the bar sink. The harder part is that you can not share a wet vent (toilet/tub) with it. Somehow the bar sink needs to tie in after the toilet.
     
  7. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    Thanks, @Stuff. To be clear, does the bar sink need a separate vent from the lav in general because of distance or is is that wet venting the toilet can only be from a lav in the same fixture group and the bar sink is not considered "in the group"? Why does that sink need to tie in after the toilet, just for the aforementioned wet venting reason? I'm IPC2012, by the way.

    <edit> after googling, is it the arbitrary "the water closet must be the last fixture in the wet-vented system" requirement? </edit>

    Here's another attempt based on the same layout, but now having only the bathroom lav wet venting the toilet. Bar sink no longer shares a drain with the lav. The lav sink, the bar sink and the tub have separate 1.5" fixture vents, as does the floor drain. Sink and tub drain branches are connected downstream of everything associated with the wet vent. All vents are connected to a common 2" above in the walls/soffit.

    All this complexity is because the bar sink isn't considered part of the bathroom group, right? Thoughts?

    Dan
    basement bathroom dimensions closeup DWV v3_cropped.png
     
    Last edited: Jul 28, 2017
  8. Stuff

    Stuff Well-Known Member

    Joined:
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    Location:
    Pennsylvania
    You are correct in that the bar sink needs a separate vent as a horizontal wet vent can only serve bathroom groups. It is not the toilet itself, the rule is "Any additional fixtures shall discharge downstream of the horizontal wet vent."
    Also you now need to be careful that you don't have a buried horizontal dry vent for the tub or floor drain.

    I don't have any ideas that would help. Hopefully someone more experienced can provide some ideas.
     
  9. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    @Stuff , thanks for the clarity. The above intends to have san-tees rolled at 45 degress at the floor drain and behind the tub, with them going up through the framing and tied to the common venting in the soffit. That's why I ran the tub drain so close to the back wall. The buried part might need to be 2" (seems ambiguous if you can do 1.5" buried or not...) but a transition to 1.5" inside the wall cavity is easy and simplies some tight routing. I believe I will need to combine the 1.5" dry vents into 2" when they combine above the bar sink drain.
     
  10. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    Still working at the best way to vent this system. I've moved all but one of the vents to the 2x6 wall for simplicity. This will keep me from having to run all kinds of vent line up the back of the tub enclosure wall, making it hard for shower built-ins, etc. The shared venting still combines and goes up towards the existing house dry vent tie-in. The tub and floor drain each get upturned san-tees in the slab and the wet venting is still isolated to the bathroom lav and wc to avoid code violation. Any comments on this one, pro or against?
    basement bathroom dimensions closeup DWV v4_.png
     
  11. Stuff

    Stuff Well-Known Member

    Joined:
    Mar 7, 2013
    Location:
    Pennsylvania
    Looking better. Some places don't want to see san-tees on their back even for dry vents. Under toilet definitely needs a wye.
     
  12. dgeist

    dgeist Member

    Joined:
    Apr 11, 2009
    Location:
    Georgia
    <grin> I can always put in a wye for a vent if they don't like san-tees...they're just longer, so I'm being frugal on space...

    As shown, the WC would drain into the arm of a combo-wye on its back with a straight stub to get it up to floor height for the flange. I had thought about rolling a 45-wye on its side and draining the wc via an elbow into the arm of that (probably draining "towards the right"). That would move all the junctions in the slab a little downstream to allow for that wye, but wouldn't really provide much benefit otherwise (except maybe giving me more room if vertical space in that area gets tight)...and I'd have to cut even more concrete. Am I missing a hidden benefit of changing the WC setup or were you just commenting that it needs to be a wye as opposed to a tee?
     
  13. Stuff

    Stuff Well-Known Member

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    Mar 7, 2013
    Location:
    Pennsylvania
    Yes, just commenting that you shouldn't use a santee under toilet.
     
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