Basement Bathroom rough-in: please check my design

[Zayd]

Good morning, folks.

I am preparing for a basement renovation project and the three-piece bathroom rough-in comes first. I'm in Michigan and my licensed plumber will do the work, but I am finalizing the fixture locations and marking the slab for the cement cutter to come and wet saw the trenches for me.

I will likely have to wet vent this bathroom through an AAV located at the lavatory. Based on my review of the code and recommendations here, I've located the fixtures so that the toilet drains last and the remaining drain piping is 2" to allow for the wet vent. As you can tell from the sketch, all fixtures are about 5-6' from the central 4" drain.

*As an aside, this will all flow to an ejector pit, which will be vented through an exterior wall, up the wall, and through the roof (I got that idea from Terry on another thread -- thanks, Terry). I am not sure if this bathroom is allowed to share that vent. If so, then it is possible to eliminate the AAV and use that instead.*

I'll be using this as my guide to marking the cement for the cutters, so I want to ensure my design passes muster. My plumber will come by for a different task tomorrow and I plan on getting his eyes in it also while he's here.

I appreciate your advice on this. Thank you!

 

[Reach4]

I think the lavatory should enter from above. So rotate your lavatory wye between 45 degrees off of plumb and plumb.
Also 3x3x2 wyes and combos are available if you want to avoid the need for the reducer.

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[Sponsor]

 

[wwhitney]

The underslab geometry you've drawn looks fine for sawcutting. A full depth smooth saw cut is a less easy surface to bond to when patching the concrete back in. So if it's possible for the saw cutter to just cut half depth (or maybe a bit less) and then just break the slab at the kerf, I think that's better.

There's no reason for the lav/shower wye to be other than horizontal. Does the ejector pit require a 4" inlet? 3" would be plenty for the 3 fixtures. It may be wise or required to provide a 3" path to the lav location to allow for a 3" cleanout there.

Cheers, Wayne

 

[Tuttles Revenge]

If horizontal wet venting then the sink connection remains horizontal is the dry vent for the entire bathroom group. And agree that you should provide a 3" cleanout there.

And your sewage ejector is going to need a vent to atmosphere so why not connect the plumbing fixtures vent to that?

 

[Zayd]

Thank you, folks. Good to hear that at least the cutting plan is solid.

Wayne, the few ejector pits I've browsed from Little Giant, Zoeller, and others have had 4" inlet hubs -- that's the reason for the 4". I supposed I can always run 3" to the pit and then adapt up to 4" once I reach the pit.

@Tuttles Revenge, I did mention that up front as an option. I'm just not aware of code requirements around that. If they are allowed to share a vent, then I can ditch the AAV.

That leads me to the second point of advice I was seeking -- the ejector pumps themselves. I had always assumed that a submersible pump was the only way it was done, then I saw mention of Tramco pumps here on the forum and looked them up. Brilliant! If nothing else, I like that the motor and pump are mounted above the pit. When maintenance is required, it's nice not to be pulling sewage-covered equipment out to service or replace it.

Are there other makers of such setups? I am not finding much in my searches, and even the Tramco pumps aren't sold by anyone but Tramco from what I can tell.

 

[Tuttles Revenge]

@Tuttles Revenge, I did mention that up front as an option. I'm just not aware of code requirements around that. If they are allowed to share a vent, then I can ditch the AAV.

Sorry.. Booster shot effects have kicked in, head is feeling a tad foggy.

UpCodes for michigan indicate special sizing / lengths for the vent, but don't seem to prohibit including the fixtures vents

The vertical pump seems interesting. I've never seen one. Looks like Goulds may make a version as well. The whole contraption will have to go through a lid that will be sealed to the riser. The lid is what I find the most unweildy aspect of sewage ejector servicing. I design mine with side discharge and venting. The lid is the same as a plastic septic tank cover so you open the lid and set it aside and all the works are easy to get to and remove.

 

[Zayd]

An update on this after my plumber came by to take a look at my plan.

His main feedback: put an AAV on everything. He's a little anal on the venting and is worried about wet venting through the lavatory, burying the lines, then having a problem later. He is willing to do it the way I've outlined above (utilizing a wet vent and 2" drains), but his recommendation is to vent each fixture individually.

My main hesitation is mostly a maintenance/being cheap thing -- I don't want to replace three AAVs every five years when I can be replacing one. But I also trust a well-executed, tried-and-true wet vent design. Should I press him on it?

 

[Zayd]

I'm considering bending to my plumber's recommendation to put an AAV on everything.

That leads to a question: can I attach vent lines to the toilet and shower drains horizontally before they turn upward in the adjacent wall? I'd think that you'd want vents coming into the top side to prevent drain water from getting in there. I know the drain water ultimately has nowhere to go up the vent, but I'm thinking of a stinky toilet slug that gets a little bit of debris in the vent and it just sits there. Or am I overthinking this?

 

[Reach4]

That leads to a question: can I attach vent lines to the toilet and shower drains horizontally before they turn upward in the adjacent wall?

No.

Within 45 degrees of plumb counts as vertical, but a dry vent cannot go horizontal under IPC.

Are you saying that your plumber does not buy into wet venting?

Sewage ejector pit needs a real vent rather than an AAV.

 

[Zayd]

Thanks for the quick answer on this, @Reach4. That may pose a problem, then. Since this is all going in slab, I don't expect that I'll have the height I need to drop the dry vent at 45 degrees into the toilet drain run and still stay under the slab, even if I go horizontal again until I hit the wall. I may be wrong on that -- I'll have to check just how low I can enter the sewage pit.

Yes, he's hesitant to wet vent under concrete since there is no remediation if it doesn't vent properly. I get his point and extra AAVs are insurance against it, but it will also complicate the plumbing in the slab quite a bit. I may be able to consolidate the toilet and shower vent to at least reduce my sawing and simplify that extra venting somewhat.

All this talk the night before I'm renting the wet saw to go at it! I thought I had this nailed down.

I appreciate your feedback.

 

[Reach4]

I expect most slab bathrooms use wet venting under the slab. If your plumber was from a place without basements he would be very used to that.

 

[Zayd]

Well, a long, hard day, but the deed is done. This picture doesn’t reflect the last bit of progress, which was chiseling out the shower area about 1.5” lower to accommodate a curbless shower.

One snag: perforated drain line presumably coming from outside the foundation (on the left) and probably connecting to a line that runs to the sump basin.

As luck would have it, its centerline is right at where Zoeller puts the 4" inlet on their sewage basins. I'll see if Zoeller can provide an undrilled basin. I think a lower inlet would work, as long as it is well above the "on" point of the pump's float. Or is there another obvious solution I should consider?

 

[Zayd]

I found a suitable solution. Jackel makes a 6" extension that attaches to the top of their sewage basins. I'll route the 3" drain underneath the perforated pipe using a couple of 22.5 or 45 elbows and meet the basin in the pre-drilled inlet hole. Then the basin extension will bring the top of the basin back up to (a little above, actually) slab level.

 

[Tuttles Revenge]

My reply didn't post, but you found a better solution for what you have. My sisters basin is about a foot below the concrete floor, we just formed up around it. But I like that the lid will be placed up higher.

I always install custom made sumps for my sewage ejectors that solves those issues. All the incoming and outgoing ports are on the side which leaves a walkable lid on top. We then typically install them under a clothes dryer so they effectively take up no space.

 

[Reach4]

I always install custom made sumps for my sewage ejectors that solves those issues. All the incoming and outgoing ports are on the side which leaves a walkable lid on top. We then typically install them under a clothes dryer so they effectively take up no space.

With the vent port on the side, do you then have a horizontal dry vent?

Having the lid with no ports, other than the power, sure seems handy for inspection and repair.

 

[Tuttles Revenge]

With the vent port on the side, do you then have a horizontal dry vent?

Having the lid with no ports, other than the power, sure seems handy for inspection and repair.

Yes. The venting can be interesting. Mostly we install a separate horizontal vent and Sometimes its a vent off the incoming drain even per the Liberty pump install directions for their lowboy model. Even the electrical comes through the side of the sump with a rubber bung and conduit. I'll have to see if I can find pics. I order the sump to spec. I get to choose the diameter and the height. They epoxy the base to the pipe at their facility and I get a gasketed lid that is the same as the green lids you see on modern septic systems.. strong enough to drive a lawn mower over.

 

[Dar Dack]

Thanks for the quick answer on this, @Reach4. That may pose a problem, then. Since this is all going in slab, I don't expect that I'll have the height I need to drop the dry vent at 45 degrees into the toilet drain run and still stay under the slab, even if I go horizontal again until I hit the wall. I may be wrong on that -- I'll have to check just how low I can enter the sewage pit.

Yes, he's hesitant to wet vent under concrete since there is no remediation if it doesn't vent properly. I get his point and extra AAVs are insurance against it, but it will also complicate the plumbing in the slab quite a bit. I may be able to consolidate the toilet and shower vent to at least reduce my sawing and simplify that extra venting somewhat.

All this talk the night before I'm renting the wet saw to go at it! I thought I had this nailed down.

I appreciate your feedback.

If building walls, why not just vent each item in the walls or share 1 with toilet/shower at least (they within few feet of each other it seems) and then tie in ceiling of bathroom or 42" above in the wall and then tie into dedicated vent for basin. My state I was allowed to tie in kitchenette 1.5" sink, 1.5" vanity, 2" shower, sump basin and 3" toilet into 1 2" vent for those 5 items and had to be under 50' though. Personally rather have regular vent than AAV and your basin has to be vented anyways, no AAV, why not just tie in.

 

[Zayd]

If building walls, why not just vent each item in the walls or share 1 with toilet/shower at least (they within few feet of each other it seems) and then tie in ceiling of bathroom or 42" above in the wall and then tie into dedicated vent for basin. My state I was allowed to tie in kitchenette 1.5" sink, 1.5" vanity, 2" shower, sump basin and 3" toilet into 1 2" vent for those 5 items and had to be under 50' though. Personally rather have regular vent than AAV and your basin has to be vented anyways, no AAV, why not just tie in.

I wish I could connect to an existing vent, but the closest one is about 50' away and would still require some first-floor demo to reveal. I asked my plumber about using the ejector pit's vent, but he was adamant that code required that vent to serve only the pit and nothing else. I still want to verify that.

I did find a way to include one more AAV. I had forgotten that there would be a short wall that sits right above the shower drain line, so I'll include another AAV there.

To be frank, I'm not sure how you can run any real venting under slab without deep-set drain lines given the 45-degree connection requirement for a dry vent.

 

[Dar Dack]

I wish I could connect to an existing vent, but the closest one is about 50' away and would still require some first-floor demo to reveal. I asked my plumber about using the ejector pit's vent, but he was adamant that code required that vent to serve only the pit and nothing else. I still want to verify that.

I did find a way to include one more AAV. I had forgotten that there would be a short wall that sits right above the shower drain line, so I'll include another AAV there.

To be frank, I'm not sure how you can run any real venting under slab without deep-set drain lines given the 45-degree connection requirement for a dry vent.

OK but if Pit in your area requires dedicated line, why not just run 2 vent lines in same area? I mean isn't the hole in your basin 10" below grade? If something is 20' away that requires 5" down at the start. Plus why worry about 45 degree, why not run a tee into wall and vent there, vent only has to be within what 5' or 6' from the fixture, or am I missing something? Like the vent for my shower/vanity is a sanitary tee in wall, the 1 part goes to sink, 1 up into wall/ceiling for vent, 1 into floor, the 1 into floor meets the drain from shower in a WYE tee, and that runs down to a 4" WYE tee from toilet (Toilet is 4' from pit so uses the pit's vent). The sanitary tee in wall is within 3 or 4' From shower and like 1.5' from vanity. A WYE can sit on it's back/side. IDK, this all passed inspection in my area. Maybe I'm thinking about this wrong, IDK, I just rather have true vents than AAV's.

 

[Zayd]

OK but if Pit in your area requires dedicated line, why not just run 2 vent lines in same area? I mean isn't the hole in your basin 10" below grade? If something is 20' away that requires 5" down at the start. Plus why worry about 45 degree, why not run a tee into wall and vent there, vent only has to be within what 5' or 6' from the fixture, or am I missing something? Like the vent for my shower/vanity is a sanitary tee in wall, the 1 part goes to sink, 1 up into wall/ceiling for vent, 1 into floor, the 1 into floor meets the drain from shower in a WYE tee, and that runs down to a 4" WYE tee from toilet (Toilet is 4' from pit so uses the pit's vent). The sanitary tee in wall is within 3 or 4' From shower and like 1.5' from vanity. A WYE can sit on it's back/side. IDK, this all passed inspection in my area. Maybe I'm thinking about this wrong, IDK, I just rather have true vents than AAV's.

As Reach4 mentioned above, the dry vent has to enter the drain line at no lower than 45 degrees from vertical. That means my drain lines need to be deep enough to accommodate that higher entry, then at least a 45-degree turn towards the closest wall, then maintain slope until it gets there, and still stay under the slab. That puts my drain lines way down and likely too deep to maintain 1/4" per foot for 20' to my basin.