Under-slab bathroom plumbing, design review, Ontario

[Ivan Blackford]

Hi All,

I'm continuing my basement plumbing project, and I'd like a review of my planned plumbing routes under the slab before I start cutting and gluing. A few notes:
1) I'm in Ontario, so I would appreciate any feedback as it pertains to the Ontario Building Code (OBC).
2) All fixtures will be dry vented, there's no reliance on wet venting or mechanical vents.
3) While not shown, I plan to use long sweep elbows to transition from horizontal to vertical when exiting the slab.
4) The existing drain is 3", the top of which is 4" below the slab at my tie-in point, so this should give me ~ 16ft of pipe length at 1/4" slope.
5) The overall dimensions of the bathroom are about 5'5" x 8'

Any help would be greatly appreciated.

Thanks, Ivan

Birdseye view of planned plumbing.

Toilet Connection

Tie-in to existing 3" Drain

Shower Pan

From left to right: Double Lav (2"), Laundry Lav(1.5"), Washing Machine(2")

 

[wwhitney]

1) I'm in Ontario, so I would appreciate any feedback as it pertains to the Ontario Building Code (OBC).

Sorry, I can't comment on the Canadian plumbing code specifically. But:

2) All fixtures will be dry vented, there's no reliance on wet venting or mechanical vents.

To do that, your vent takeoff has to be on the upper half of a horizontal pipe, and then the dry vent has to rise vertically (which includes up to 45 degrees off plumb) until at least 6" above the fixture flood rim. So no horizontal dry vents below the slab, not even for half the length of a fitting.

Given that, your shower dry vent takeoff needs to be changed. And your WC connection doesn't show any vent.

Or you could rely on wet venting for the shower and/or WC. That might require reconfiguring where the washing machine and laundry sink tie in. It would in the US, but IIRC the Canadian plumbing code has a limited allowance for other fixtures to flow through a horizontal wet vent. You'd have to check whether it would cover both the washing machine and laundry sink, or only one of them, or none of them.

Cheers, Wayne

 

[Sponsor]

 

[Ivan Blackford]

Thanks for the feedback. Assuming I make the following couple of changes, is this acceptable?

Green lines represent proposed changes.

I appreciate all the feedback, thanks again!

Ivan

 

[wwhitney]

Still not following what you have in mind for the WC. If the barrel inlet of the 3" wye is your dry vent, that doesn't work (plus you only need a 1.5" or 2" dry vent, depending on Canadian plumbing code). The barrel inlet is horizontal, but the takeoff has to be vertical.

On the shower, if I understand your green lines correctly, that idea works, except that you have the wye takeoff backwards. Water that gets into the vent should not be directed to drain back towards the trap.

Cheers, Wayne

 

[Ivan Blackford]

Still not following what you have in mind for the WC. If the barrel inlet of the 3" wye is your dry vent, that doesn't work (plus you only need a 1.5" or 2" dry vent, depending on Canadian plumbing code). The barrel inlet is horizontal, but the takeoff has to be vertical.

On the shower, if I understand your green lines correctly, that idea works, except that you have the wye takeoff backwards. Water that gets into the vent should not be directed to drain back towards the trap.

Cheers, Wayne

Ah yes, I drew the wye direction backwards for the shower, sorry. For the toilet vent, I plan to use a 3x1.5x3 fitting, with the takeoff angled up 45 degrees, similar to this, but without the horizontal section (all vent lines will be either 45 degrees or vertical).

 

[Ivan Blackford]

Additionally, I think the OBC allows for a 1.5 in vent for a toilet:

 

[wwhitney]

For the toilet vent, I plan to use a 3x1.5x3 fitting, with the takeoff angled up 45 degrees, similar to this, but without the horizontal section

You mean a 3x3x1.5 fitting, the first number is the straight outlet, the second the straight inlet, the third the side inlet.

That works if you are using a 3x3x1.5 combo. It also works if you are using a 3x3x1.5 wye as in the picture (without the horizontal portion), although your elbow to go vertical will end up being a 60 degree bend. That means the vent takeoff is really only 30 degrees, and so not technically vertical. But it seems to be common in the plumbing industry to overlook that deviation, so it would be fine.

Cheers, Wayne

 

[wwhitney]

Also, because you reposted that picture with the horizontal 3" wye and the closet flange right next to it, I just wanted to comment that to dry vent the WC the vent takeoff needs to come off before the WC fixture drain joins any other drains. If the WC fixture drain joins another drain first, that drain needs to wet vent the WC, and any downstream dry vent takeoff would be superfluous.

Cheers, Wayne

 

[Ivan Blackford]

Good point, I was thinking of that. How close to the closet flange can I put my wye for the vent connection? For a normal trap, I need to be 2x pipe diameter away from the trap weir, but I am not sure how close i can be for a toilet, as the trap is in the toilet, not part of my installed plumbing.

 

[Jeff H Young]

Good point, I was thinking of that. How close to the closet flange can I put my wye for the vent connection? For a normal trap, I need to be 2x pipe diameter away from the trap weir, but I am not sure how close i can be for a toilet, as the trap is in the toilet, not part of my installed plumbing.

no minimum distance on the toilet to the vent

 

[Ivan Blackford]

I have glued up my plan for the WC branch, the WC vent, and the start of a branch going off to the left for the shower/lav/laundry. I am venting the WC through the wall behind the toilet, all vent sections are on a 45 angle or completely vertical. Any comments would be appreciated. Thanks, Ivan.

 

[Jeff H Young]

what I see looks good shower laundry, and lav yet to be seen

 

[Ivan Blackford]

Thanks! Another (somewhat related) question. I will be creating a network of horizontal 1.5" vent piping at the ceiling level. When branching off horizontally on the vents, should I be using WYEs, or are sanitary tees permitted?

Ivan

 

[wwhitney]

Thanks! Another (somewhat related) question. I will be creating a network of horizontal 1.5" vent piping at the ceiling level. When branching off horizontally on the vents, should I be using WYEs, or are sanitary tees permitted?

For connections at least 6" above the fixture flood rim, you can use any pattern fitting you like. San-tee would be simplest, but if for some reason that little bit of curvature was a problem, you could use a vent-tee.

Cheers, Wayne

 

[Reach4]

Thanks! Another (somewhat related) question. I will be creating a network of horizontal 1.5" vent piping at the ceiling level. When branching off horizontally on the vents, should I be using WYEs, or are sanitary tees permitted?

Ivan

When using a santee to branch off horizontal venting, invert the santee from its normal orientation when used to carry drainage. It's not that it won't work either way, but your work will look better if you do it that way.