New basement plumbing layout

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kubo777

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Hi,

I am looking for some feedback on the proposed layout.
I would like to add a basement bathroom and kitchenette. Bathroom will be located underneath the main floor bathroom, next to main stack and main vent. Bathroom will have shower, lavatory, toilet. Kitchenette in next room will have a sink.
The main stack currently serves toilet, vanity and bathtub from the floor above (main floor).

1. Are there any issues with the proposed layout as shown? Any recommneded changes?
2. Is it ok to tie the venting for the 0_LAV and 0_KS to the main vent stack at high ceiling in the basement?
3. If I was to re-route main floor bathtub (OPTION 2), and drain it to 2" drain serving the 0_KS, can the 0_KS be wet vented this way, and have the vent continue and go up to roof (or tie it to existing main stack vent in the attic for venting)?

Thanks.
 

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wwhitney

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Nice system for labeling the fixtures.

Questions 2 and 3 first: there is no wet venting allowed between floors (unless the Canadian plumbing code has something unexpected), and the only way to conventionally dry vent fixtures in your basement is to run at least one separate dry vent pipe up through the first floor. That basement dry vent can connect to a dry vent on the first floor, but not to any portion of a stack that is carrying drainage. In other words, for usual dry venting there must be an air path from the basement dry vents to the roof that doesn't see any drainage.

If your Canadian plumbing code allows AAVs, then using one or two AAVs in the basement would be an alternative to adding that dry vent riser up to the first floor.

Question 1: once you have the dry venting sorted out, you'll need two dry vent connections for the basement fixtures, one for the lav and one for the kitchen sink. If conventional dry venting, those two vent risers can combine in the basement ceiling and then proceed to the riser through the first floor. Or if AAVs are allowed, you could use two AAVs.

The following drain connectivity order would be an allowable horizontal wet vent under US and Canadian coodes, starting at the lav: lav, then shower, then WC, then kitchen sink. One US code (IPC) would allow the order of shower and WC to be swapped, as you have it; you'll have to check your Canadian code to see if that is allowed. Neither US code would allow the kitchen sink to come in second as you have it, but IIRC the Canadian code does allow a separately vented fixture to drain through the horizontal wet vent like that. But please double check.

Cheers, Wayne
 

kubo777

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Thank you for the thorough reply.

I might have not included all relevant info before, so I am attaching a pic showing my current plumbing connections in the basement room. After breaking up the concrete this weekend, I uncovered old 3" toilet drain that got abandoned and covered by previous owners. The drain was vented by the 2" (reduced to 1½") copper vent that runs up alongside the main stack (which I have previosuly thought was vent stack tied to main stack under the slab, its purpose at the time escaped me). I highlighted it with red line.

I presume at some point on main floor, at high level, the vent stack ties to the main stack before reaching the roof. The fixtures on main floor shoudl have their vents tied to this vent (again, I presume as that's the only thing that makes senese). There is only one 3" vent coming up in attic in this area, and only one 3" roof penetration.

Now back to my layout.
My revised plan would then be to replace existing 3" copper TEE (that fed the toilet) from main stack with 3" TEE with 2" side inlet.
2" would drain the shower. The 2" shower line would be vented similarly to current configuration, using 2" WYE with pipe reconnected to existing copper vent. This would provide dry vent for shower, and allow the rest of basement fixtures to vent thru this as well.

Next, run 3" pipe from the TEE as per previous diagram. The toilet would be wet vented thru 0_LAV. 0_LAV and 0_KS would have dry vents up to basement ceiling, then tied to existing copper vent stack.

Does this confirguration adress the issues beofre, or do I need to change anything ?
Thank you.

Existing.jpg
 

wwhitney

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Thoughts on your picture: what I see there is a 3" drain coming down from above; a san-tee where the 2" drain connects to a 1-1/2" dry vent, for connecting a lavatory; and the 2" dry vented lav drain connecting to the 3" horizontal drain to wet vent the WC, before they both join the 3" drain from above.

Also, now is the time to check all of the buried copper DWV to see if it is still in good shape, and to replace it with plastic if not.

As to your layout, since that you have a presumed 1-1/2" dry vent available next to your 3" stack, you certainly can use that for dry venting the shower. You'd do that by using a 2x2x1-1/2" combo with the 1-1/2" side branch vertical, and that dry vent would need to stay vertical until at least 6" above the shower flood rim.

As for wet venting the WC via the lav, with the layout in the OP, you'll need to confirm that the dry vented kitchen sink is allowed under the Canadian plumbing code to flow through the wet vent, but IIRC it is. By dry venting the shower, there's no longer any question of the fixture order.

As to the connections at the main stack, seems to me that the new 3" horizontal basement branch will end up much lower at the stack that your current connection. So I'd suggest just stacking a 2" san-tee and a 3" san-tee. You also have the option to connect the new 3" horizontal basement branch to the 3" horizontal building drain (which you labeled to street), and/or connecting the 2" vented shower drain to the 3" horizontal basement branch instead of to the 3" stack, should either of those be easier.

Cheers, Wayne
 
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