Vertical venting

[Jimdel]

Terry,

Can you please review my PlumbingLayout.png file? I'm trying to wet vent the upstairs bathroom based on the other attached file Hammerpedia.png. It is not clear to me how his example is venting the toilet (3 DFUs) plus the lav and tub (for a total of 7 DFUs) with a 2" vent pipe. My plan may look involved, but I have existing HVAC and joists I'm trying to avoid. I've attached a 3rd file, Framing.png, showing the overall remodel with the existing framing (I know that I have to add additional joists in the existing open stairwell that is shown). Overall, I'm trying to minimize the DWV piping and fixtures I'll use.

Thanks,
Jim

 

[wwhitney]

It is not clear to me how his example is venting the toilet (3 DFUs) plus the lav and tub (for a total of 7 DFUs) with a 2" vent pipe.

In the example, if you consider the stack from the top to bottom, it has 4 sections:

Dry vent: venting 6 DFUs (WC, lav, tub)
Upper wet vent: venting 5 DFUs (WC, tub) with 1 DFU of drainage (lav)
Lower wet vent: venting 3 DFUs (WC) with 3 DFUs of drainage (lav, tub)
Lower drain: draining 6 DFUs (WC, lav, tub)

The size of the wet vent portion depends on the DFUs of drainage, not the total DFUs of drainage plus venting. So the lower wet vent portion only needs to be 2". If there were also a shower between the tub and the WC, then the wet vent between the shower and the WC would be carrying 5 DFUs of drainage while venting the WC. That wet vent section would therefore need to be 3".

As to your rendering, you have two issues:

1) The bathtub trap arm can not turn downward to join the stack. The bathtub is depending on the lav for its vent, and other than WCs, the vent for a trap must come off before the trap arm falls more than one pipe diameter. So if space permits, you could raise the lowest horizontal section of the lav (ideally eliminating that vertical jog in the middle of the lav horizontals) and hit the stack with a san-tee for the bath tub.

2) Your downstairs WC is not vented. It can be wet vented by bathroom fixtures, but not by a kitchen sink or a bath sink. You don't show what is coming in on the 3" line on the bottom left, but any horizontal wet venting is restricted to drain segments carrying only bathroom fixtures. Is there a lav for the WC? If it is properly vented and its drain joined the WC before any non-bathroom fixtures came in, then the lav would wet vent the WC.

Cheers, Wayne

 

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[Jimdel]

Wayne,

Thanks for your response. I've attached a revised version that includes individual vents for everything except the first floor toilet, which I vented via the upstairs toilet vent.

I also attached an image with some second floor framing shown. Do you think I should route the upstairs lav drain as shown by the red arrows (to tap into the tub drain)? I believe I could then wet vent the double vanity via the tub vent if I increase the vent pipe to 2". Am I correct? I don't know if I'm getting too many bends in the double vanity drain.

In your opinion, do I have too many pipes/fittings for what I'm trying to do? I am quite constrained by having existing double joists on top of walls (so I can't go vertically through the wall) and on top of a metal beam (so I can't go down through them). I keep trying to come up with ways to wet vent fixtures, but I'm not having any luck.

Thanks again,
Jim

 

[wwhitney]

OK, in your last diagram you have a problem with the upstairs tub and WC vents. A dry vent can't go horizontal until 6" above the fixture flood rim, so certainly not below the floor. The typical way to do a dry vent-takeoff is to route the trap arm (or WC fixture drain) under or very close to a wall and have the vent rise straight into the wall.

However, the red lav drain routing you show in the framing layout would take care of that. It would let you wet vent the tub and the WC, eliminating both of the problematic dry vents.

Downstairs you've taken care of the WC venting by wet venting it with the lav. To double check, the fitting where the lav drain joins the WC drain should be a combo; the rendering looks more like a san-tee on its back, which is not allowed for drainage.

The downstairs lav vent routing is obviously complicated, and with the upstairs WC dry vent eliminated, maybe you can find a simpler way to route it to the upstairs lav dry vent. And of course you do have the option to use an AAV for the downstairs lav. If you keep the vent through the roof for the downstairs lav, it's worth considering if you can get the kitchen sink and/or bar sink vent to easily join the lav vent in the ceiling framing above, to eliminate one or two AAVs.

Cheers, Wayne

 

[Jimdel]

Wayne,

I think this may do it. Originally, I was including the dual lav DFUs in the wet vent pipe size calculation instead of realizing it was dry venting the dual lav. Please let me know if this looks OK to you.

Oh, I guess I need to replace ALL my sanitary tees with combos? I didn't know they weren't allowed in drainage systems.

Thanks for your help,
Jim

 

[wwhitney]

Everything looks fine. A couple comments:

Originally, I was including the dual lav DFUs in the wet vent pipe size calculation instead of realizing it was dry venting the dual lav. Please let me know if this looks OK to you.

On wet vent sizing, what matters is the DFUs of drainage the wet vent is carrying, not the DFUs of fixtures the wet vent is venting. [Well, that matters too, but the former basically always controls, as there's a special sizing rule, versus the latter, which is the same sizing as a dry vent.]

On the downstairs lav, the wet vent for the WC is only carrying 1 DFU of drainage, so that lav's drain and vent could both be 1.5" under the IPC. [2" minimum for the UPC.] The upstairs double lav, that wet vent is carrying 2 DFUs of drainage up to the tub, so it needs to be 2" as drawn, although the dry portion could be 1.5" [2" minimum for the UPC.]. Then the wet vent portion between the tub/lav and the WC is carrying 4 DFUs (a tub is 2 DFUs), which is the maximum allowed for a 2" wet vent, and 2" is still fine.

Thus the downstairs lav wet vent, and both lav dry vents, could be reduced to 1.5". But I'm not saying you should, just that you can if there's an upside to downsizing. For example if either vent has to be routed through 2x4 load bearing studs, I see an advantage to the smaller vent size.

On the tub trap arm, though, I see an advantage to a 2" trap and a 2" trap arm. Maybe just a quirk of mine, 1-1/2" is allowed.

Cheers, Wayne

 

[Reach4]

If this is new piping, I would upsize the pipe below the kitchen santee to 2 inch. Kitchen sink drains are more likely to clog, and that would often be where the piping goes from vertical to horizontal.
https://terrylove.com/forums/index.php?threads/kitchen-drain-size-ipc-in-ct.26591/

You might also consider a cleanout above or below the kitchen santee. Above is better if readily accessible, but below is still very good.

 

[Jimdel]

Ok, THIS should be the final version. Can you please check the fittings? I used combos and wyes in all the drains. I have all the 2nd floor combo connections in the wet vent set at 0 degrees (horizontal) based on a JLC article (picture attached).

For the 1st floor, are the wye and combo connections for the WC wet vent being set at 45 degrees OK?

With your help I have gotten rid of lots of extraneous pipes and fittings - much appreciated.

Thanks,
Jim

 

[Reach4]

Not yet. Bring the lower floor lavatory drain to join the toilet waste before the toilet waste joins the kitchen or upstairs waste.

 

[wwhitney]

And for classic horizontal wet venting, the downstairs lav should join the downstairs WC with a horizontal wye.

Also, where you write "at 0 degrees" each entry has to have at least 2% slope, so I think it ends up more like 1.5 degrees.

Lastly, where the drainage is turning from horizontal to fall vertically, you don't need a long sweep 90, a regular quarter bend is OK.

Cheers, Wayne

 

[Jimdel]

Attached are an Upstairs and Downstairs file incorporating your feedback: 1. Changed the downstairs lav (bar sink) to WC connection to a horizontal wye; 2. Replaced upstairs long sweep 90 with a regular quarter bend on the upstairs 3" horizontal to vertical transition; 3. Moved the downstairs bar sink discharge to the WC discharge pipe.

I've included a sump pump discharge (from the basement) - I had forgotten to include it until I went downstairs to check something.

Should I replace the combo fitting at the kitchen sink/lav discharge with a Wye fitting since it is now serving as a wet vent for the sump pump (per your "classic horizontal wet vent" comment)?

Do you think I should include a cleanout plug upstream of the downstairs WC? I plan on putting one upstream of the kitchen sink/lav connection to the main 3" drain pipe.

I understand your comment regarding fittings not being at actual 0 degrees, I just want to make clear whether I have the fittings placed in the horizontal plane or rotated 45 degrees.

Thanks again for all your help,
Jim

 

[wwhitney]

I'm a bit confused by the new downstairs configuration. As I understand it there are 4 fixtures: kitchen sink, bar sink, lavatory, and WC. To wet vent the WC, you can only use the lavatory drain, not the kitchen sink or the bar sink. Joining a sink to the WC drain as shown, before either fixture joins any other drains, is the correct approach to wet vent it, but the sink has to be the lavatory. Your latest drawing labels it bar sink.

The sump pump is collecting groundwater, correct? If so, does your jurisdiction really allow you to pump that into the sanitary sewer? Far more common to my understanding is to discharge it on the ground away from the house, or into a drywell away from the house.

If you are allowed to put it in the sanitary sewer, you would need a standpipe and a trap (just like a washing machine), and the trap would need a vent. Speaking of washing machine, I don't see any in your diagram?

On the "classical horizontal wet vent" comment, I myself don't see any reason why the lav/WC wye for wet venting couldn't be vertical instead of horizontal, both in terms of function and code rules. But as it is traditionally horizontal, that's a safer choice, some might object to its being vertical.

Cheers, Wayne

 

[Jeff H Young]

The reason for wye on side might be so he can reach a wall to bring the up. bar sink not quite legal . if the wye could have been vertical, it would not be a problem except its going to a bar sink

 

[Reach4]

Looks good for the area you covered.
Rather than a sump pump, you probably want a sewage pump. If you might add a toilet later, make that a grinder pump.

And I think that pump would go into a sealed pit, which receives the kitchen waste. That pit would have a VTR (vent thru roof).

 

[Jimdel]

The sump pit is actually a concrete pit that receives discharge from a basement sink. It does not receive groundwater.

I don't dispute your answer, but it seems like a tortuous dishcarge path for the pump to pump water vertically up from the pit, and then have to do a 180 turn into a standpipe which then turns another 180 degrees thru a trap. Is a standpipe required, instead of a true connected pipe, in case there is a clog - so the pump will just overflow the standpipe instead of burning itself out?

Thanks

 

[wwhitney]

Any connection to the building drain needs a trap to block sewer gases from entering the home. If you have a check valve in the vertical piping from your pump in the pit up to the building drain connection, then the standing column of water would also function to block sewer gases. However, I don't think that's recognized as a trap, since it relies on a mechanical component (the check valve). So if you need a trap, you need a standpipe.

There is a style of pump designed for utility sinks that mounts under the sink in place of the trap, with no basin (or a very small internal volume in lieu of a basin). Of the instructions I've read for that style of pump, they always end with "Connect the discharge piping to the building drain." I'm not sure what the listing of that type of pump covers and how it works code wise without any trap. Perhaps the design of the pump and the outlet piping geometry would allow it to function as a trap even if all the mechanical components failed, and it is listed appropriately.

Cheers, Wayne

 

[Jimdel]

I've included an enclosed drain basin in the basement that collects water from the basement sink via a P-trap. The basin is dry vented, which prompted me to dry vent the first floor toilet (since I can't use the bar sink as it''s wet vent) and dry vent the bar sink. The bar sink dry vent is > 6" above the bar sink drain.

 

[Jeff H Young]

jimdel your vent tie ins need to be 6 inch minimum above flood level not 6 inch above drain

 

[Jimdel]

Oops - thanks.

 

[Jimdel]

Is this a legal way to wet vent a tub and toilet via a lav? I haven't seen any code that says I can't have the lav wet vent attach to the Vertical toilet discharge instead of Horizontally. I am trying to avoid some HVAC ductwork.

Thanks