Will my plumbing system work?

[Mayo]

I'm new to plumbing and installing the drain system myself. I have a crude drawing of what I planned out and wanted to get opinions on if it is vented correctly.

In the diagram I have a wet vent from the sink. Would this system work?

 

[wwhitney]

The shower needs to join downstream of the lav/WC connection. Then it works as long as the shower trap arm (from the trap outlet to the wye where it joins the combined lav/WC) falls no more than one pipe diameter, while falling at least 1/4" per foot.

Cheers, Wayne

 

[Sponsor]

 

[Mayo]

The shower needs to join downstream of the lav/WC connection. Then it works as long as the shower trap arm (from the trap outlet to the wye where it joins the combined lav/WC) falls no more than one pipe diameter, while falling at least 1/4" per foot.

Cheers, Wayne

Thanks for the response, so its a 2 inch shower pipe. That means the distance from the trap outlet to the wye can't be any longer than 8 feet?

 

[wwhitney]

Correct. And that 8' limit is also spelled out separately in the IPC (which Michigan uses), but it's just the logical result of the two other rules I mentioned. Also, 8' is possible only if you get the 1/4" per foot slope perfect, no more no less.

Cheers, Wayne

 

[Mayo]

@wwhitney I have another bathroom setup for the second floor if you don't mind taking a look at it?

It's a little trickier due to show the shower hooks up. I'd imagine the wet vent for the toilet is fine, but the shower might be an issue?

 

[wwhitney]

The above diagram is fine, the shower trap arm is just from the trap to the end of what you've correctly labeled as the wet vent. The tricky part there is having the combined branch (lav/WC/shower) turn down at exactly the same point where the shower meets the lav/WC.

Cheers, Wayne

 

[Mayo]

The above diagram is fine, the shower trap arm is just from the trap to the end of what you've correctly labeled as the wet vent. The tricky part there is having the combined branch (lav/WC/shower) turn down at exactly the same point where the shower meets the lav/WC.

Cheers, Wayne

Awesome thanks for the feedback! Is it that tricky to get the shower to turn down at the same point? Can't I just use a T? Or is the tricky part that its unlikely the shower and WC/lav pipe line up perfectly.

 

[wwhitney]

Awesome thanks for the feedback! Is it that tricky to get the shower to turn down at the same point? Can't I just use a T?

Certainly not a san-tee with the barrel horizontal. That orientation is only allowed for drainage when the side entry points straight up and is a dry vent takeoff. [And only the IPC allows that, the UPC would require a combo for that purpose.] Otherwise the barrel on a san-tee carrying drainage has to be vertical (which allows for up to 45 degrees off plumb).

They make a fitting called a "double quarter bend" which would work but it's not 100% clear whether that would be OK for the shower wet venting. You could use a double san-tee or double fixture fitting and just cap the top entry, although that would be strange (but fine IMO).

The standard way to do it would be to approach the WC and the shower each offset from each other and from the stack below. Then one turns with a LT90 to point towards the stack; the other joins with a combo; and then a quarter bend to turn down to the stack. But that requires a fair amount of width and wouldn't all fit in one joist bay.

Cheers, Wayne

 

[Mayo]

The standard way to do it would be to approach the WC and the shower each offset from each other and from the stack below. Then one turns with a LT90 to point towards the stack; the other joins with a combo; and then a quarter bend to turn down to the stack. But that requires a fair amount of width and wouldn't all fit in one joist bay.

I'm a little confused by this and drew a diagram, is this what you were describing? Does the shower still wet vent off the WC/Lav?

 

[wwhitney]

As an isometric, I meant something like below. Where the black lines are all horizontal and in the same plane (other than the 1/4" per foot pitch), and the red line is vertical. And where I've drawn LT90s and combos as having a little 45 degree segment to show that they could be (2) 45s or a wye plus 45, respectively. [But where the black horizontal turns down to the red vertical, I drew a sharp corner to show that a quarter bend is allowed there.]

But I'm not saying that you have to do it that way or you should do it that way. Just that if it's convenient to do it that way, it's definitely a normal and correct way to do it. The complication with your original drawing is that usually with horizontal wet venting, when the shower drain joins the drain wet venting it (lav/WC in your case), the outlet is horizontal.

Cheers, Wayne

 

[Mayo]

I see what you mean now and makes sense. However, I may not have that much room available for all the connections required.

Could I connect the shower and WC with a double fixture fitting and then vent off of that? This way the shower has its own venting but then the WC will have that vent and the original wet vent.

 

[wwhitney]

Once you wet vent the WC with the lav drain, there's not much upside to adding a dry vent to the lav/WC. But if it's convenient to pass the shower trap arm under a wall between the drain and the stack location, then just dry venting the shower with a vent in that wall would be fine.

I think further discussion would be best with a floor plan of the bathroom, showing the fixture locations, which way the joists runs, the walls, and where the stack below needs to be (or the whole wall below if it's flexible).

Cheers, Wayne

 

[John Gayewski]

As an isometric, I meant something like below. Where the black lines are all horizontal and in the same plane (other than the 1/4" per foot pitch), and the red line is vertical. And where I've drawn LT90s and combos as having a little 45 degree segment to show that they could be (2) 45s or a wye plus 45, respectively. [But where the black horizontal turns down to the red vertical, I drew a sharp corner to show that a quarter bend is allowed there.]

But I'm not saying that you have to do it that way or you should do it that way. Just that if it's convenient to do it that way, it's definitely a normal and correct way to do it. The complication with your original drawing is that usually with horizontal wet venting, when the shower drain joins the drain wet venting it (lav/WC in your case), the outlet is horizontal.

Cheers, Wayne

View attachment 86362

Unless the pipe is upsized here that vertical wet vent section could cause problems with the two 90's when the toilet is flushed. 90's do close themselves off from air flow when vertical. Meaning air needs to come from somewhere which would be the shower trap arm.

 

[John Gayewski]

 

[wwhitney]

Unless the pipe is upsized here that vertical wet vent section

Sorry my isometric isn't clear. I think you missed my commentary: "the black lines are all horizontal and in the same plane (other than the 1/4" per foot pitch), and the red line is vertical." So there is no vertical wet vent section.

I was just showing that the WC/lav drain needs to use a LT90 (or two 45s) to make a horizontal to horizontal bend, and given the angles I chose for the two perpendicular horizontal directions, the short diagonal section seemed to end up drawn at the same angle as a vertical. Which is why I added the color coding to distinguish.

Cheers, Wayne

 

[John Gayewski]

Sorry my isometric isn't clear. I think you missed my commentary: "the black lines are all horizontal and in the same plane (other than the 1/4" per foot pitch), and the red line is vertical." So there is no vertical wet vent section.

I was just showing that the WC/lav drain needs to use a LT90 (or two 45s) to make a horizontal to horizontal bend, and given the angles I chose for the two perpendicular horizontal directions, the short diagonal section seemed to end up drawn at the same angle as a vertical. Which is why I added the color coding to distinguish.

Cheers, Wayne

I'm used to reading an iso traditionally. Verticals are vertical. All horizontal should be fine.

 

[wwhitney]

I'm used to reading an iso traditionally. Verticals are vertical.

Verticals are vertical, but not everything vertical is a vertical. : - )

When you have two different angles on the page for the two horizontal axes, then some horizontal direction at an angle between those two axes is going to end up running up and down the page. Which make it indistinguishable from a vertical.

But maybe it's incumbent on the person making the drawing to pick a point of view that minimizes horizontals that end up running up and down the page. Plus I'm not sure I got all the angles on the page correct anyway, so maybe that horizontal at a 45 shouldn't have ended up running up and down the page.

Cheers, Wayne

 

[John Gayewski]

Verticals are vertical, but not everything vertical is a vertical. : - )

When you have two different angles on the page for the two horizontal axes, then some horizontal direction at an angle between those two axes is going to end up running up and down the page. Which make it indistinguishable from a vertical.

But maybe it's incumbent on the person making the drawing to pick a point of view that minimizes horizontals that end up running up and down the page. Plus I'm not sure I got all the angles on the page correct anyway, so maybe that horizontal at a 45 shouldn't have ended up running up and down the page.

Cheers, Wayne

45's are shown with dashed lines in an iso drawings. The dashed lines extend in the two directions a 90 would follow if that makes sense.

A vertical 45 would end up between the two points that a horizontal and vertical 90 would end up, which makes only true verticals vertical. Up is up and down is down but some ups don't go all of the way up, lol.

 

[wwhitney]

45's are shown with dashed lines in an iso drawings.

Thanks, that's a useful convention that I haven't seen before. Is it specific to the plumbing industry? I'm more familiar with isometrics of 3-d objects, where dashed lines indicate hidden edges.

Cheers, Wayne

 

[John Gayewski]

Thanks, that's a useful convention that I haven't seen before. Is it specific to the plumbing industry? I'm more familiar with isometrics of 3-d objects, where dashed lines indicate hidden edges.

Cheers, Wayne

I'm not sure really. Dashed lines do show hidden lines also. Any of the few drawing interpretation classes I've had do have some slightly contradictory info in them. Where one symbol can mean slightly different things. You can also show similar things with thinner lines I believe, which would also be how to show dimensions. I worked on a fab shop for a while and we got some pretty complicated drawings for welded pipe assemblies. Without the dashed lines some of them would be too ambiguous.