Dishwasher Draining Into Basement Laundry/sink System - Venting? - Plumbing - DIY Home Improvement | DIYChatroom

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Old 03-19-2012, 12:58 AM   #1
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Dishwasher draining into basement laundry/sink system - venting?

I have this existing system (in black) and new plumbing I am thinking of putting in in blue(s). In Ontario with the new wet venting rules, the dark blue may not be required (but putting in all the blue isnt that big a deal). Just wondering if this is correct or what (though I need to know a few min/max distances in my diagram - like what should K-KK, A-AA, A-D be?).

[In retrospect rereading the Ontario wet vent guidelines, since D is 1.5", I dont think wet venting can be used here, so all the blue plumbing must go in.]

Another question is - the vent pipe that runs/will run V-B-D - Im pretty sure it used to just have a dishwasher drain hose in it at B from the old owners. Totally not to code (and partly dangerous, the gap between hose and inside wall of pipe was stuffed with fibreglass insulation, yikes! Either not acting as a vent OR releasing sewer gas...)

Anyway, is there a chance that D, running into the floor ISN'T attached to the drainage system? Where would it go to? (Into foundation?) Obviously very bad if anything drained into it (though you'd think a high flow rate would fill it up within a few seconds. Should I try that with a hose?) If that were the case, perhaps it's safer to put a double T at F or H for the dishwasher? Much trickier to get in there to do that however.

I just realised that D may be a floor-laid revent, like kitchen islands use. (It's odd to have two drains into the floor anyway, one would be a vent...). That'd make this all slightly more to code, but the top of B smells of sewer gas when my temporary restuffing of insulation is removed, so it cant be correct...) - but if D is a floor revent (wet revent from the main stack..?) what does that do for me?

[ Ontario new wet venting: page 20+ ]

Going to be fun getting the vent up to the attic/roof too. Sorely needed for the 3 fixtures/appliances - the main house stack is 12 feet away and cast iron, so I'd rather just go to the roof (the walls line up above this system nicely, inside of a closet 2nd floor, basement landing 1st floor, still a bit of work though). Guess Ill be learning about venting out the roof soon!


Last edited by mathx; 03-19-2012 at 01:06 AM. Reason: wet venting comment w.r.t. size of drain/vent
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Old 03-22-2012, 01:54 PM   #2
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With more thinking about this, and checking for and finding a cleanout in the basement floor for the D 'drain', I'm pretty sure this is a revent back to the main stack. Water poured down it was visible at the cleanout heading towards the stack.

However, to keep this simple and more clearly to code, Im doing two things:
- keeping it dry
- not relying on it as the only vent

This results in:

I can't be 100% sure its to code as a vent at D's attachment to the main stack (diameters of pipe, where it attaches, etc), though it was put in place as such for the drainage by previous owners. Failing that, adding an AAV at the top of its extended vertical portion at B ensures proper venting. Putting B through to the roof would be hard - penetrating the roof is my biggest worry (not to mention getting that much vent pipe up between the walls for 2 floors). Ill replace H with a san-T (double Y) which I believe is required by code, even though the laundy nor the washer (even if draining together!) could wash a 1.5" pipe fully.

Any comments?


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basement , dishwasher , laundry , vent , venting

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