Rough in drain basement layout

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wintersoldier

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I have broken up the concrete in my basement for a new bathroom. There are drains that have been roughed in by the builder, but the layout won't work for us so I'm going to rearrange.

Hopefully the picture can give an idea of which way the drains are going. I've attached a picture showing the preferred locations for the toilet, sink, and shower.

Would the drain layout work? I added a vent in green for the shower, but unsure if it is needed. A few people I have talked to have said it is needed, and others have said with horizontal (wet) venting, it is not required.

There is already a vent established as the 2 inch pipe is going up the wall to what I assume is eventually through the roof. Is there a better layout that would make use of just the existing 2 inch vent by the vanity?
 

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wwhitney

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Dry venting a shower like that is not allowed--a dry vent takeoff has to be vertical (at most 45 degree from plumb) and stay vertical until 6" above the flood rim. So you can't run a dry vent horizontally under the slab.

The dry vented lav can wet vent the shower and the WC. You'll need to check the Canadian plumbing code on whether that would require the lav to join the shower first, and the WC afterwards, or if it doesn't matter. The US plumbing codes differ on that point.

If you're not subject to a restriction on the order of fixtures in a wet vent, then something like the drawing below would seem more obvious and direct. If the WC does have to come last, something more complicated will be required.

Cheers, Wayne

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wintersoldier

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Dry venting a shower like that is not allowed--a dry vent takeoff has to be vertical (at most 45 degree from plumb) and stay vertical until 6" above the flood rim. So you can't run a dry vent horizontally under the slab.

The dry vented lav can wet vent the shower and the WC. You'll need to check the Canadian plumbing code on whether that would require the lav to join the shower first, and the WC afterwards, or if it doesn't matter. The US plumbing codes differ on that point.

If you're not subject to a restriction on the order of fixtures in a wet vent, then something like the drawing below would seem more obvious and direct. If the WC does have to come last, something more complicated will be required.

Cheers, Wayne

View attachment 94494


Thanks for the reply Wayne.

Based on Ontario code it appears that the WC has to be downstream of other fixtures:



(1) A soil or waste pipe may serve as a wet vent provided that,

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


Based on this I'm a bit lost of how proper venting can be established.

Something like this?

I feel like there should be an easier way than what I have laid out.
 

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wintersoldier

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Thanks for the reply Wayne.

Based on Ontario code it appears that the WC has to be downstream of other fixtures:



(1) A soil or waste pipe may serve as a wet vent provided that,

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


Based on this I'm a bit lost of how proper venting can be established.

Something like this?

I feel like there should be an easier way than what I have laid out.


And another layout.
 

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wwhitney

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Based on this I'm a bit lost of how proper venting can be established.
Two wet vent options come to mind:

1) If the branch drain (that blue pipe you need to tie into) is sufficiently deep, you can pass the lav drain over the top of the WC drain. The WC drain just goes straight to the branch drain. The lav drain goes towards the shower drain and connects to it (there is a limit on the distance from the shower trap to the wye where the lav joins the shower, as the lav drain is the vent for the shower, and so the shower drain up to that wye is the shower trap arm.) Then the lav/shower together fall slightly and join the WC/branch drain.

2) If that's not possible, the lav drain will have to pass around the WC to the left, so it can hit the shower before they jointly hit the WC. That's a bit like your drawings, but your drawings have a loop in the drain. There's no loop in the drain, that's not how wet venting works. Take a look at my drawing for reference.

Or you could dry vent the shower. For example, if the boundary of the shower facing the WC is a solid wall, from the shower trap you can send the shower drain towards and under that wall, take off a dry vent via an upright combo with vertical side branch going into the wall, and then have the dry vented shower drain join the WC. It can join the WC before or after the lav does; either dry vented fixture can wet vent the WC, and whichever one hits it first will do the job.

Cheers, Wayne
 

wintersoldier

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Thanks Wayne. How about something like this? Trying to go by your option of going to the left of the WC. I'll have to make the shower drain sweep a bit more when it ties into the 2" from the lav (provided this is allowable to begin with).
 

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wwhitney

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Thanks Wayne. How about something like this?
That works in principle. A few comments:

1) Why is the shower drain drawn thinner than the lav drain, isn't it also 2"?

2) The length of that thinner segment (the shower trap arm) is limited, you need to check the Ontario Plumbing Code for the maximum allowable length. Also, it needs to fall at least 1/4" / foot, but it may not fall more than one pipe diameter. That gives you an upper bound (8' for a 2" pipe at exactly 1/4" / foot) but some plumbing codes impose a length limit below that.

3) You'll get a simpler final result if you remove the white elbow (22.5 degrees?) on the blue pipe and tie just downstream of it.

4) The lav drain route is a bit awkward, so the left-right segment you drew at the very top of the picture might be best done above the slab in the wall near the bottom

5) Rearranging the bathroom fixtures might simplify your DWV layout, but I imagine you've already considered the tradeoffs involved.

Cheers, Wayne
 

wintersoldier

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That works in principle. A few comments:

1) Why is the shower drain drawn thinner than the lav drain, isn't it also 2"?
- the current roughed in drain from the builder is 1.5", however I believe I can do 2".

2) The length of that thinner segment (the shower trap arm) is limited, you need to check the Ontario Plumbing Code for the maximum allowable length. Also, it needs to fall at least 1/4" / foot, but it may not fall more than one pipe diameter. That gives you an upper bound (8' for a 2" pipe at exactly 1/4" / foot) but some plumbing codes impose a length limit below that.
- it is either 6' or 8' in the code, regardless the distance with the longer shower run is about 5.5' in my layout

3) You'll get a simpler final result if you remove the white elbow (22.5 degrees?) on the blue pipe and tie just downstream of it.
- yes will likely go that route

4) The lav drain route is a bit awkward, so the left-right segment you drew at the very top of the picture might be best done above the slab in the wall near the bottom
- didn't even think of that. will help reduce the amount of concrete to jack up.

5) Rearranging the bathroom fixtures might simplify your DWV layout, but I imagine you've already considered the tradeoffs involved.
- limited by headroom with the heat runs so this was the only layout that gave more head room for the shower.
Cheers, Wayne

Answers in bold above. Appreciate the quick replies.
 
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