Basement Bathroom with Ejector Pump - Rough in questions

Velvet Hammer · Jan 19, 2011

Hello all! I'm roughing in for a basement bathroom. I have some questions about DWV layout and potentially using an AAV to vent the bath group.

I know that the ejector will need it's own 2" through the roof, but I was hoping to keep the toilet, lav and shower on 1 AAV under the sink.

Also, if someone could advise if the layout of the pipes works? I know there are some restrictions with what is downstream of what, etc...

Cacher_Chick · Jan 19, 2011

The use of an AAV in that manner will be entirely up to your local inspector. Here, the wet vent on the lav has to be 2"

If I were going to be running a vent for the basin, I wouldn't even consider not running a vent for the rest of it. It's just not good plumbing.

Sponsor · 2022-01-29T12:20:58-0800

Velvet Hammer · Jan 19, 2011

Thanks for the replay, cacher!

I do want to plumb this using best practices, not just to pass inspection.

Can you clarify this: "If I were going to be running a vent for the basin, I wouldn't even consider not running a vent for the rest of it. It's just not good plumbing." Are you saying that you'd vent the shower, lav and toilet independently? OR Are you saying to vent 2" to the lav and go all the way through the roof?

My biggest challenge is that the bathroom is sunk 24" lower than the rest of the basement... the back wall of the entire bathroom is 3 cinderblocks with 2x4 framing from there up (vents in the "wall" wouldn't work).

As you can see in the picture, I can run pvc up the wall behind the shower and / or to the right of the toilet (where the basin is) ...

Please let me know your thoughts, or how you would recommend plumbing it - Thanks so much!

-Dave

Cacher_Chick · Jan 19, 2011

The answer depends on if you are allowed to wet vent the shower and WC. You will need to submit an isometric diagram of your proposed plumbing for the permit, and the inspector can tell you if the wet vent will be allowed. Some places also require a floor drain.

The shower enclosure will need to go into a framed alcove anyway, so if you frame the back wall down to the floor, there will be no problem running the vents. The fixture vents can run horizontally once up near the top of the wall and tie together into one stack going through the roof.

If that is an outside wall, I would put at least 2" of extruded polystyrene foam board against the concrete for insulation and vapor retarder.

Velvet Hammer · Jan 19, 2011

The framing is all done and yes, there is lumber all the way down to the slab on the 5' wall, so I can vent in there. To avoid confusion, I'd like to "aim" for the most logical layout. Would it make sense to run a 3" 'main' from the basin (far right) to the 2x4 shower wall (far left) with a 2" vent up that wall and then just wye in the toilet, sink and shower? (as seen in the attached "underneath" diagram... kind of.)

I'd still throw in an AAV under the sink if you think it may help?

Again, thanks for offering your knowledge!

Dlarrivee · Jan 19, 2011

I'm confused once again, as to why people have such an obsession with these AAV units...

If you're going to run the vent for the basin through the roof, why on earth would you not simply tie into that with your vent for the bathroom group?

Can anyone give me a good reason?

hj · Jan 20, 2011

1. You do not need, nor would you want, 3" between the connection and the lavatory tee.
2. Run the vent up in the cabinet and offset into the wall above the concrete blocks, then connect it to the pump's vent.

Velvet Hammer · Jan 20, 2011

dlarrive - I was not aware that AAVs were seen in such a negative light. I figured that if it would allow the proper venting and was easier, it was a no brainer. Apparantly you disagree. If that is the consensus, I will avoid AAVs whenever possible. Is it really inferior? Or perhaps a culture shift that hasn't caught on yet? What will the system lack if the aav was used?

hj -

1. I assumed 3" was required because the shower uses a 2" and the lav would dump into that - so I thought it made sense to upsize. Also, it would be wet venting the toilet... Why is oversize bad?

2. I was under the impression that the pit needs its own DEDICATED vent that cannot be tied into any other vents. Is that NOT true?

I don't have a large cavity to get from the basement to the roof - I figured 1 less 2" going up would make life that much easier.

Either way, my last diagram has a 2" vent going up behind the shower wall - so if I ran another vent up the block and behind the sink wall to tie into the shower vent - then ran ran that parallel to the pit vent and tie into existing vents in the attic... would that work?

Velvet Hammer · Jan 20, 2011

Would this be preferred? Please let me know if there is anything that should be done differently!

Cacher_Chick · Jan 20, 2011

No vent can run at less than a 45 degree angle until they are at least 6" above the flood rim of the lav. In your drawing it appears the shower vent is horizontal under the floor, which is a no-no. It would need to come directly up from the drain line and into the stud wall.

If the wet vent is permitted there, you should be fine wet venting the shower through the lavatory and then the separate shower vent would be unnecessary.

The offset on the lav will need to be at least 45 degrees also.

I would shoot a 2" for the basin and a 2" vent for the fixtures. Run them up into the attic and then tie together into a 3 or 4" through the roof.

Velvet Hammer · Jan 20, 2011

OK - I feel like I'm getting close! It seems like my first post is the closest, except replace the lav 1.5" & AAV with 2" that extends all the way through the roof... Right?

Are the pipe sizes in the floor correct? Should it be 2" or 3" between the toilet wye and the lav/shower wye? (hj said 3" there was NG, but if its for the shower, lav and wet venting the toilet, I'm not sure it's 'too big' ??)

Also, I was under the impression that the ejector needs a dedicated vent through roof - cannot be tied into other vents... thoughts?

Dlarrivee · Jan 20, 2011

The ejector basin itself needs a proper atmospheric vent because it needs to be able to displace air out of the basin and draw air into the basin as the liquid level changes.

AAVs are generally perceived as a "half-ass" or "lazy" way of plumbing something. I'm quite certain that as long as you tie the vent for the basin together with the vent for the wet vented bathroom group the proper distance above the flood level of the sink you'll be allowed to tie all of it together and only go up with ONE 2" line to vent the whole deal.

Where I'm from you need a 2" vent to wet vent a bathroom group. I'm not sure about your latest drawing because you cannot have a "flat vent" for your shower... The vent needs to come off at 45* or greater and cannot be anywhere near horizontal until you get above the sink, as cacher-chick stated. I think you should revert back to wet venting everything through the lav, just make sure you use 2" above the san-tee for your lav and I'd want a cleanout below that T.

You're almost there.

Edit: Oh and the other reason, (I'm not alone on this) AAVs are not the greatest is because they eventually fail, and need to be accessible, I see no reason for creating a point for failure when it would so simple to vent properly.

Velvet Hammer · Jan 20, 2011

Last question (maybe): Are the pipe sizes in the floor correct? Should it be 2" or 3" between the toilet wye and the lav/shower wye? (hj said 3" there was NG, but if its for the shower, lav and wet venting the toilet, I'm not sure it's 'too big' ??)

Dlarrivee · Jan 21, 2011

What good would a 3" line do there? You only need 3" downstream of the w/c...

hj · Jan 21, 2011

Your horizontal shower vent is NOT an improvement. "Oversizing" drain lines reduces their velocity and "self scouring" effect. Oversized drains can plug up worse, and be more difficult to unplug, than properly sized ones. It is a local requirement, but when we installed basement ejectors, the vent for the pit and the fixtures were tied together and then connected to the vents for the rest of the plumbing.

Velvet Hammer · Jan 21, 2011

With all of your advice, the project has started! Please see images and let me know your thoughts... The first is a mock up of the drains and the second is where 2 vents tie into 1 and make some tricky turns - there's a bit of cement there, but none of it is in permanently. Please let me know if there are too many turns in this vent line (at ceiling height) for code.

Cacher_Chick · Jan 21, 2011

A few thoughts-

You should look at the instructions for your shower. Most showers require a stud wall on 3 sides, from top to bottom. You will need to know exactly where the shower will be in order to properly line up the drain & trap.

Any PVC you have put together without glue will go into the fittings further when you glue it, so all your lengths will be wrong if you are dry-fitting.

Many inspectors will look to see that every joint has a ring of primer around it as proof that the joint was primed & glued. Some will want to see the info printed on the pipes facing outward so they can easily verify you are using approved pipe.

Vents flow upward, so it looks like you have the sani-tee at the ceiling facing the wrong way. The cleanout does not appear to be a cleanout tee.

When you start trenching, you should find a footing under those concrete blocks. The width of that footing will determine where the pipe can be put in. If that "wall" is considered stuctural, you cannot trench within 45 degrees of the bottom of the footing.

Velvet Hammer · Jan 21, 2011

We're going to use toggle bolts or similar to connect the pan to that block wall... and I traced the drain ring onto the concrete to get the rough lines drawn for the trenching (which is now done.)

I know that the glued PVC will change the length of the runs - that mock up was just to post a picture on this here!

Regarding the flow of the vents, I found a few pictures online of vents tied together with downward flow, but I'll turn it over...

See san-tee in top right: http://lh3.ggpht.com/_z4zRfcPf25I/S3jTsaF57pI/AAAAAAAABMw/SsQD701kLJ8/s800/revised DWV.jpg

Any you're right, the clean-out isn't threaded. Would have been interesting when I tried to close it up! Thanks!

I'm really hoping that wall is not considered bearing, as the pit is right there...

Thanks again for the input - if anybody else has any criticism, I'm all ears! Otherwise, I'm gluing it up on Sunday.

Velvet Hammer · Jan 23, 2011

I have another question for you experts... I have a 3 inch copper drain right next to the location of my ejector, but there is already an upstairs toilet and lav feeding this - I'm guessing that this is too much volume to add the ejector to this line... Is that correct?

If I didn't feed into that 3", could I run the 2" discharge all the way to the main stack - approx 30' away? I'd run the discharge straight up for 10', and then with drainage slope for the 30'. Would this cause any issues with code/performance?

My other option is to feed the 2" into a new 3", but the clearance for that isn't really there ... 2" would make the job much easier. Thoughts?

Next question: there is a 1/2" copper hot water supply line feeding an upstairs half bath. Can I tap into that to feed my shower and lav, or is that too much demand on the 1/2" copper? Will it fail, or just drop in pressure when everything is in use??

If I end up running new water supplies, what size Pex should I run for the hot and cold? Without your input, I'd run 3/4" for cold and break off 1/2" tees for the toilet, lav and shower and 1/2" for hot for the lav and shower... Is this best practice??

Thanks!

Ballvalve · Jan 24, 2011

Lot of cement to break. I would raise the floor and use a shorter turn on the toilet flange, or one with the turn incorporated for tight spots.

Basement Bathroom with Ejector Pump - Rough in questions

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