Basement bath vent locations

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Mwatkins

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I’ve inherited a basement finishing job that I'm unsure of how to vent.

My mom bought a home that was built in 1945, 5 years ago the old homeowner found a crack in the cast iron stack where it entered the concrete floor in the basement and was leaking. It was removed and all plumbing was then replaced with new pex water lines (house also had galvanized water lines at that time) and ABS drains/main stack. Due to the damage from the leak they gutted the basement and were planning to remodel, but never got around to it. When they had the plumbing replaced, they opted to rough in a 2nd bathroom for the house in the basement.

Fast forward 5 years and now this is my problem. I've attached a quick sketch of the layout I'm dealing with. The question I haven't been able to answer is how they planned to vent the new bathroom. Being an older home, the only vent is via the main stack that is between 8' to 14' feet away of the new bath, I have found that they added air admittance valves to the laundry riser and the kitchen sink, so my gut is telling me this was their plan for the basement bath.

In addition to this, they have been pumping a condensate line for the air conditioner through the ceiling to the laundry riser. They're also running the water softener drain the same way. I'd like to remove this line and add in a riser (shown in green) in the utility area by tapping off the shower drain. Is this even possible?

My thoughts are:

1: Vent lav and toilet via air admittance valve in the vanity
2: Vent shower via air admittance valve in wall it shares with linen closet
3: Tie into shower drain with new riser for water softener and condensate pump

Am I heading in the right direction here?

Unfortunately adding a new vent to the system will require some serious surgery and is pretty much off the table unless there is absolutely no other way to make this happen.

Thanks,

M.
 

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wwhitney

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So the blue is existing? It's set up for a dry vent at the lav to wet vent the WC and the shower. That is, as long as the shower trap arm (from the shower trap to the wye where it joins the 3" line) is no more than 8' in length and falls no more than 2". Utah appears to be on the IPC, so you can use an AAV at the lav.

And the green is something new you'd like to add? It will need its own vent, which also could be an AAV. And then the question is where you tie the green drain into the blue. You can't tie into a drain before it is vented. So if you tie in downstream of the 3x2 wye for the shower meeting the WC/lav, that's fine. If you want to tie into what would otherwise be the 2" shower trap arm, you'll need to separately vent the shower, and then tie into the 2" line downstream of that vent takeoff.

Cheers, Wayne
 

Mwatkins

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Hello Wayne, thanks for responding.

So the blue is existing? It's set up for a dry vent at the lav to wet vent the WC and the shower. That is, as long as the shower trap arm (from the shower trap to the wye where it joins the 3" line) is no more than 8' in length and falls no more than 2". Utah appears to be on the IPC, so you can use an AAV at the lav.
Correct. The blue is the current rough in that is in the concrete. I'm having to make educated guesses as to placement based off of the fresh concrete repairs from where they did the rough in. Based off of this, it appears that I'm right at 8' from the shower trap to the wye on the 3" drain from the WC. As for slope I'm going to guess that we're looking at no more than 2" due to this being a basement and within another 8' of the main drain line heading to the street.

So my thinking that I can vent via AAV at the lav is correct.

And the green is something new you'd like to add?
Correct again.

It will need its own vent, which also could be an AAV. And then the question is where you tie the green drain into the blue. You can't tie into a drain before it is vented. So if you tie in downstream of the 3x2 wye for the shower meeting the WC/lav, that's fine. If you want to tie into what would otherwise be the 2" shower trap arm, you'll need to separately vent the shower, and then tie into the 2" line downstream of that vent takeoff.
For whatever reason, they didn't rough the shower trap in place. They left a hole in the concrete with the 2" drain capped horizontally in it, so I will need to place the trap. The downside is that in order to tie a new line in below where the shower trap is, I'll have to cut into the concrete to make the connection. The upside is that if I'm reading your reply correctly, I should be able to place a wye for the shower drain and add the trap, then upstream from there, add another wye for an AAV and the new water softener drain. Correct?

Thanks again for the reply, I really appreciate it. I've reached out the former owners to see if they have any photos of the rough in that might be able to help clarify what is now in the concrete.

Best,

M.
 

wwhitney

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For whatever reason, they didn't rough the shower trap in place. They left a hole in the concrete with the 2" drain capped horizontally in it, so I will need to place the trap.
That's a good thing, as it lets you fine tune the trap inlet location to line up precisely with your shower drain.


The upside is that if I'm reading your reply correctly, I should be able to place a wye for the shower drain and add the trap, then upstream from there, add another wye for an AAV and the new water softener drain. Correct?
That depends. What do you have in mind for the softener drain? If it's going to be a floor drain, then you have the option of putting the trap at the same height as the shower trap. That would let you join the floor drain and shower drain, and vent both drains with one AAV, anywhere that's within 8' of both traps (assuming a 2" floor drain). The AAV would have to be 4" above the drain, so presumably in a ventilated box within a wall that the drain passes under.

If you have in mind a standpipe with a trap above the floor (what my original response was based on), then that trap needs a vent before the trap arm falls one pipe diameter, i.e. a vent takeoff and AAV above the floor. Then the drain needs to join the existing drains. As a standpipe is not a bathroom fixture, if the drain joins within the bathroom group, it would disrupt the wet venting of the shower. So either the standpipe drain would have to run separately to the 3" line, to a new wye downstream of 3" wye where the shower joins the WC/lav. Or the shower would need its own AAV, and the standpipe drain could then join the shower drain downstream of that AAV.

Cheers, Wayne
 

Mwatkins

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Or the shower would need its own AAV, and the standpipe drain could then join the shower drain downstream of that AAV.

Cheers, Wayne

I was thinking more along the lines of option 2 with a standpipe above the floor in the adjoining utility room...Specifically what you're saying here.

I'm definitely more visual in my thinking so I've attached another quick sketch of what I think you're saying for clarity.

In the sketch, I have 2 wye's on the 2" shower drain before it connects to the 3" drain. The downstream wye would connect to the new standpipe and trap in the utility area. The upstream wye connects the shower trap and an AAV in wall for the shower. Have I interpreted what you've said correctly?

If so, does it matter how much elevation gain the new standpipe drain has? That is, it will exit the concrete and run for 6-7'or so before terminating into the trap and standpipe. As such I'm going to see a gain in elevation of 4-5" over that of the shower drain. Is this a concern?

Thanks again for all your help.

Best,

M.
 

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wwhitney

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Your drawing is not very clear, but there's definitely a couple problems:

A vent connection for a trap has to be at an elevation before the trap arm has fallen more than one pipe diameter. So with an above floor standpipe trap, the standpipe AAV would have to come off the horizontal trap arm before the drain turns down into the floor.

A dry vent can't be horizontal unless it's at least 6" above the flood rim level of the fixture. So you can't continue the shower drain away from the 3" line into a wall to add an AAV. The only way to dry vent the shower drain is if the drain passes under (or close enough to) a wall between the shower drain and the 3" line.

Your best bet if you want the standpipe is simply to leave the blue alone, don't add any of the green, put the standpipe AAV in the utility room with the standpipe, and break concrete to run the standpipe drain over to the 3" drain, downstream of all the bathroom fixtures.

Cheers, Wayne
 

Mwatkins

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Your drawing is not very clear, but there's definitely a couple problems:

A vent connection for a trap has to be at an elevation before the trap arm has fallen more than one pipe diameter. So with an above floor standpipe trap, the standpipe AAV would have to come off the horizontal trap arm before the drain turns down into the floor.

A dry vent can't be horizontal unless it's at least 6" above the flood rim level of the fixture. So you can't continue the shower drain away from the 3" line into a wall to add an AAV. The only way to dry vent the shower drain is if the drain passes under (or close enough to) a wall between the shower drain and the 3" line.

Your best bet if you want the standpipe is simply to leave the blue alone, don't add any of the green, put the standpipe AAV in the utility room with the standpipe, and break concrete to run the standpipe drain over to the 3" drain, downstream of all the bathroom fixtures.

Cheers, Wayne
Ok, this is sounding like much more brain damage than it's worth.

Think we'll be leaving the softener and condensate pump as is and moving on with life.

Thanks again for all the help.

Best,

M.
 
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