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Old 02-08-2012, 12:54 AM   #1
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Shower Addition to Bathroom - Drain Tie-In Question (B.C.)

Hey all. I'm undertaking my first major renos at my place and am looking to install a shower in an existing bathroom. I have attached a picture below of my intended layout. Blue is the existing lavatory connection to a 2" stack, red is the toilet connection to the 3" stack. The question is, can I tie the shower drain into either the 3" or 2" stacks without an additional vent (wet venting I believe)?

As best I can tell after polking a few holes here and there and going into the attic, the two stacks tie together and are vented through a single 2" vent. The run to the 2" stack (the further of the two), is about 6' from the intended shower drain. The 3" line has one more toilet from the upper floor tied to it, and the 2" line has a tub/sink from the upper floor, and a kitchen sink on the other side of the main floor bathroom (pictured).

I'm located in B.C., Canada...any help is appreciated. And let me know if I can provide any further info.
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Old 02-08-2012, 11:21 PM   #2
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Looks like you cannot vent through the toilet as under our code the WCs must be installed downstream of all other fixtures. And your upstairs WC on the the 3" stack makes it a non starter.

Now the issue with the sink stack is that by adding the shower you'll be just over the allowable hydraulic load when wet venting, tub or sink (1.5 fu) from the upper floor + and a kitchen sink (1.5 fu) + new shower (1.5 fu) = 4.5 fu when the maximum fu (fixture units) allowable on a 2" vent is 4.

The best option seems to be is to add another vent, unless you want to upsize existing vents to accomodate this new shower. Where in the house is this new shower located?


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Old 02-09-2012, 12:47 AM   #3
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Thanks for the reply. After cutting into the bulkhead in my kitchen (here we go!), I've discovered that at least the upper bathroom lavatory is tied to the 3" stack. There are two vents in the attic that come from the back side of the bathroom (I'm assuming toilet and shower?) and these tie into the main vent stack.

So this should mean that tying the shower into the 2" stack should be fine - correct? I'm actually within 5' of the stack as well, which I found out is code for wet venting.

Oh and as for bathroom location, it is literally in the center of the main floor (3 storey house). It probably wouldn't be incredibly hard to add a vent, as there is a closet in the room above it that I could chop into, but I'd rather not if its not necessary. Thanks!
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