Side inlet sanitary tee into horizontal soil stack

[tvier]

Hi all, I ran into (another) complication with my bathroom reno.

I'm adding a shower to a bathroom that already has a bath + wc + lav. I thought I had it figured out, but after more demo I realized the main stack wasn't set up as expected.

The toilet is on a short branch to the the main stack, along with the lav + bath. This branch goes directly into a ~3' long horizontal section of the soil stack. My initial plan was to use a side inlet tee, but with the horizontal section I'm not sure if that's a good idea.

How should I tie the shower drain into stack?

I've attached images of the bathroom layout, and the current plumbing setup.
Other relevant info: I'm in Ontario, this is a top floor bathroom, and the distance from the new drain the the existing tee is 4'.

 

[Breplum]

Not UPC already. lav and tub should tie in after the vent and the vent is supposed to be a combo not a tee. Consider hiring a pro.

 

[Sponsor]

 

[tvier]

I should have mentioned that the tub already has it's own vent, and the lav will be in the future as well. They're too far from the stack to vent that way anyways.

I thought the tee would be fine since the vent above is dry? Maybe I should have labeled the picture better. Either way, there's lots of room so I'm happy to switch it out.

There are a bunch of other issues with this bathroom that aren't anywhere near code, like the tub vent going horizontal right after it's takeoff and an s-trap on the lav. I've got those figured out, but this one is a little less clear to me.

 

[tvier]

It was this thread from @wwhitney that I was thinking of

IPC may allow a sanitary tee on its back for a vent take off with the drain remaining horizontal; UPC requires a combo there, and I think a combo is better.

I thought I remembered that Ontario matched the IPC on this one, but I'll dig in a little more. It might be pretty tricky to fit a combo when I put the walls back.

 

[wwhitney]

Making a few assumptions about Canada's plumbing code, to be verified:

- san-tee on its back is OK for vent takeoffs
- a full-size main vent through the roof is required
- the minimum size for a horizontal wet vent carrying more than 1 DFU is 2".

In which case even if the tub and lav are properly vented before coming into the picture in the OP, that looks like a 1-1/2" drain line carrying them? That would not be large enough to allow it to act as a wet vent, and the WC should be vented before or as it joins another drain (unless there is a Canada exception to this).

Looks like you are redoing this area. So why not move the tub and lav to join downstream of the san-tee on its back? And then join the shower after that. Or if the shower is joining in from the same side as the tub and lav, and if the trap is close enough, and if the tub/lav drain is large enough, the shower could join the tub/lav first and be wet vented by the tub/lav.

As to the idea of replacing the san-tee on its back with a san-tee with side entry, that doesn't work. The curvature on a san-tee is insufficient for a horizontal-to-horizontal change of direction.

You might be able to use a combo or wye with side entry, using the side entry for the vent takeoff. But I've quite understood the proper use of those fittings, as the side entry has no curvature at all. Seems like using them with the side entry vertical as a vent is the only possibility that could make sense, though.

Cheers, Wayne

 

[tvier]

Thanks Wayne, that was great.

That would not be large enough to allow it to act as a wet vent, and the WC should be vented before or as it joins another drain (unless there is a Canada exception to this).

I was fixated on the toiled vented using the main stack (since that's how I thought it was set up before I removed the floor) but that clearly doesn't work as you pointed out.

So why not move the tub and lav to join downstream of the san-tee on its back? And then join the shower after that.

That sounds like a good solution (and is basically what @Breplum said, so thanks there too). If I understand the set up correctly:
- the stack vent is venting the wc
- I'll need another vent for the new shower
- the tub and lav still need their own vent

All that should be no problem

 

[wwhitney]

If I understand the set up correctly:

Certainly it works to provide individual dry vents for the lav, tub, shower, and WC (the main vent for the WC). And those individual vents can go horizontal and connect to the main vent at an elevation at least 6" above their respective fixture flood rims (and 6" above the WC flood rim).

But if you want to use horizontal wet venting, you could reduce that to just providing individual dry vents for the lav and the WC. Check your wet venting rules.

Cheers, Wayne

 

[tvier]

Ah right, with the tub+lab coming in after the WC that would provide the wet vent. I'd have to up the size of the drain from the vent to the stack to 2" right?

I'll make sure to double check the wet venting rules

 

[wwhitney]

Ah right, with the tub+lab coming in after the WC that would provide the wet vent. I'd have to up the size of the drain from the vent to the stack to 2" right?

I'll make sure to double check the wet venting rules

If the shower (or tub for that matter) joins downstream of the main vent, then the question is whether Canada's rules allow a dry vented WC drain to wet vent another fixture. In the US, one primary code (UPC) does not; the other (IPC) does.

If a WC drain is allowed to wet vent another fixture, then the next question is whether the fixture drain from the trap (of the tub or shower) to the 3" horizontal drain meets the limits on length and total fall (which is one trap diameter) for a trap arm. If not, a dry vent takeoff would be required within the specified distances from the fixture trap.

[The above applies if the tub or shower connects directly to the 3" drain. If the dry vented lav joins the fixture drain first, then the question is whether the resulting trap arm complies with the specified distances, and whether the lav drain is properly sized to act as a wet vent. Again in the US, the two different codes differ on whether that minimum lav drain size is 1-1/2" or 2" if acting as a wet vetn.]

Cheers, Wayne

 

[tvier]

That's very clear, thanks.

My local inspectors are pretty responsive. I'll draw up a plan and run it by them.

 

[Reach4]

The Ontario Building Code | Wet Venting

(d) the water closets are installed downstream of all other fixtures,

(e) trap armsand fixture drains connected to the wet vent do not exceed 2 in. in size, except for connections from floor drains in accordance with Clauses 7.5.1.1.(3)(a) to (c),

 

[tvier]

Thanks for doing the reaseach for me! Point (d) makes it clear I can't wet vent, so dry vent it is.

Does point (e) cause any problems? It seems I would be fine, since we're after the vent for the WC and the shower drain would be 2". It doesn't make any difference to what I do, just curious.

 

[wwhitney]

Does point (e) cause any problems?

If you are not using wet venting, point (e) is a non-issue.

Point (d) precludes using the 3" vented WC as a wet vent. But you could still use the lav drain to wet vent the tub or shower or both.

Cheers, Wayne

 

[tvier]

Passed the inspection using the dry vent setup. Thanks for the help all.