Drain sink in to toilet vent?

bobvilasJune 22, 2012

I had installed a 3" line for a toilet at our new pool house. Now my wife wants a sink. Can I drain the sink into the 2" vertical vent for the toilet. (see drawing)

I am in Hawaii and we are under 2006 UPC.



Thank you for reporting this comment. Undo

First off,,, the vent connection at the watercloset(toilet) will not pass code.

Need more information before I can offer you a solution.

    Bookmark   June 23, 2012 at 10:38AM
Thank you for reporting this comment. Undo

Thanks lazypup.
The toilet rough already passed inspection and is in slab.
I was mostly curious about draining the vanity into the 2" vent. I can add a clean-out to the lav vent as you suggest.

    Bookmark   June 23, 2012 at 8:53PM
Thank you for reporting this comment. Undo

There are actually three points in question here so I will take them one at a time.

The reason that I asked you what fitting was under the WC (Toilet) is that in your drawing it shows a short stub of line extending upstream from the WC closet flange connection where the 2" vent is attached. If it was done in that manner it would not pass began that short 4" or 5" of horizontal pipe where the vent is attached would be a horizontal dry vent, but code prohibits any horizontal dry vents until the vent reaches an elevation at least 6" higher than the highest fixture served by the vent.

Code also requires that a WC must be attached to the upstream end of the line, (except a low heal inlet or side inlet closet bend may be used if the inlet is serving another fixture-- Many local codes prohibit low heal & side inlet closet bends).

In your corrected drawing the vent is attached downstream of the closet bend, which is the way it should be.


UPC code table UPC T 7-5 lists lavatory drains & traps at 1-1/4" and the code will allow us to increase the size of the drain by one nominal trade size, so the horizontal drain line in your drawing that is running from the lav location to the vent riser should be 1-1/2", not 2" if you are only installing a single lav, however, if you are installing two lavs the line would then have to be 2" because under the UPC an 1-1/2" line is limited to 1dfu, and lavs are rated at 1dfu so if you had two lavs the combined load would be 2dfu's and require a 2" line.

Next let us discuss your lav location. If you are connecting the lav to the 1-1/2" vent riser on the left your fine, but if you are attaching it to the horizontal line that you have shown as 2" be careful here. The lav fixture arm needs to be connected to the upstream end of the line and the vertical vent needs to be attached downstream of the lav fixture arm.

The UPC allows an 1-1/2" trap arm to be a maximum of 3'6" from the trap weir to the vent opening. Allowing an estimated 18" from the trap weir to the drain line, you can easily see that your vent connection could still be up to 2' downstream from the lav fixture arm.

Not that it really matters but FYI, once you attach this new drain line to the 2" vent riser from the WC, the portion of line from this connection to the roof would still be classified as a vent, but the line from this connection down to the WC would then be classified as a "Combined waste & vent".

The difference is that a "vent" is always dry, whereas once you connect the lav, the lower section of pipe serves as a vent to the wc but when water is discharged from the lav it serves as a drain so it is called a combined waste & vent.

    Bookmark   June 24, 2012 at 5:55AM
Thank you for reporting this comment. Undo

Thanks lazy for the help!
Really appreciate it.

So if I am hearing you correctly, I need to have the vertical vent downstream of the fixture arm for the Lav. See amended drawing?

What direction should the clean-out point? Towards the roof vent or towards the Lav?

Do I need another clean-out lower in the system?

    Bookmark   June 24, 2012 at 3:31PM
Thank you for reporting this comment. Undo

There is quite a bit of information to cover here so I prepared an illustration that should help you follow along.

First off, let us discuss how fittings are identified.
As you know, PVC pipe is used for both pressure pipe in water supplies and DWV (drain,waste & vent) applications, however the fittings used for DWV are dramatically different from pressure fittings, by example, at a change of direction a pressure fitting will have a sharp change in direction whereas a DWV fitting will have a radius curve.

In the plumbing trade in order to insure we are specifying the correct part all pressure fittings are defined by the actual number of degrees represented by the change in direction I.E. a 45deg Elbow or 90deg elbow but for DWV instead of saying elbow the fitting is defined as a "Bend" and the actual change of direction is specified as a fraction of a circle. A full circle has 360deg so a DWV 90deg elbow would be called a 1/4 bend (1/4 of a circle) and a 45 deg DWV elbow would be called an 1/8bend.

Although it is called DWV today, years ago all waste and drain lines were called "Sanitary Lines" so often DWV tee's are listed as Sani-tee's.

Note in the illustration where I show the new vent line connected to the drain via a "Wye & 1/8bend". Code prohibits installing a sani-tee on a horizontal line. Code requires that we install a wye, which would direct any flow in the downstream direction, however the side inlet of a wye is at a 45deg directon and you want to tie your vent in at 90deg so we would install the wye, then add an 1/8bend on the wye to complete the 90degs.

You could use a wye and a standard 1/8bend, but an 1/8 bend has a female hub on both ends so you would have to install a short nipple of pipe to connect them. An esier method is to use a "Street 1/8 bend". A "Street" fitting has a female hub on the input end and a raw pipe or spigot end on the discharge end, so a "street 1/8bend" would fit right into the hub of the wye without needing a nipple. (a nipple is a short length of pipe equal to or less than 12" long). An even simpler method would be to use a "Combo" which is a Wye & 1/8 bend made up in one fitting.

Now let us discuss where to connect your new vent. The line size is 1-1/2"dia and the UPC will allow the trap arm for 1-1/2" to be up to 3'6". We measure the actual length of the pipe beginning at the "trap weir". The minimum allowable distance is 2x the pipe diameter so you may attach your new vent at any convenient location with is greater than 4" and equal to or less than 3'6" from the trap weir to the vent opening.

Now let us discuss cleanouts. Code requires a cleanout on the upstream end of all lines plus at every change in direction which is 45deg or more. (there are some exceptions to that rule but for now let us concentrate on that part.)

You do not need a cleanout on the bottom drain line because you have a trap adapter & a removable trap. Code allows a removable trap to be used as a cleanout, but careful here. If you opt to install a glued in trap you will also need a cleanout.

At the top of your new auxilliary vent you will need to install a sani-tee with the horizontal line to the main vent connected to the side opening of the tee. You then install a female thread adapter on the top of the sani-tee and put a male plug in it. That is your cleanout.

You also need a cleanout on the upstream end of the upper horizontal vent. To make a cleanout there you install a "test Tee", which is a tee that has a female hub on both ends but the side inlet is FIP (female iron pipe thread). You could then screw a male plug in the inlet or you could use an ordinary sani-tee and install a female thread adapter and plug.

Here is a tip....
When defining the size on a tee, if all the openings are the same size it is listed with one size, by example a 2" tee, but they also make reducing tee's, which means the openings may be different sizes. For reducing Tee's the order of listing is 1. the straight through input, 2. the straight through outlet and 3, the side opening.

You are attaching 1-1/2" pipe to a 2" pipe so you could use reducing tee's. For your application you would need 2 each 2"x2"x1-1/2" sani tees.

    Bookmark   June 25, 2012 at 3:53AM
Thank you for reporting this comment. Undo

Sorry to dig up an old thread, but I found it on a google search. I'm a little new to this but I'm going to start a project soon and so I've been doing my research.

I'm a little confused about the use of cleanouts. I've been reading up on 2009 UPC so maybe it's different for the 2006 or something, but why would you need a cleanout on a vent line? On a side note, I think I remember reading cleanouts were needed for every 135 Deg, not 45.

    Bookmark   January 14, 2013 at 7:27PM
Sign Up to comment
More Discussions
Marble shower panels valve replacement :( !!!
We have a couple of bathrooms with a single handle...
Vamsi Kodavanty
Fed up and ready to tackle my well water issues
I've been reading posts trying to educate myself for...
New Water Softener problem (Fleck 5000 ProFloSXT)
Hello, I recently moved into a home that uses well...
Under counter water filters…again
I've lurked here for over a year and have learned so...
Water Softener - Help with Proper System Selection
Hello, I decided to put in a water softener system...
Sponsored Products
Finn Single Hole Lavatory Faucet with Pop-Up Drain
Signature Hardware
Contour Toilet Brush Set
$7.99 | zulily
Thermocast Kitchen Inverness Drop-in Acrylic 25x22x9 2-Hole Single Bowl Kitchen
Home Depot
23" Flue Extension for Casa Series Stainless Steel Island Range Hoods
Signature Hardware
KOHLER Bathtubs Mariposa 5.5 ft. Left Drain Bathtub in Sandbar K-1224-VBLW-G9
Home Depot
Yosemite Home Decor Seats Molded Elongated Closed Front Toilet Seat with Slow
$21.60 | Home Depot
Barclay Products Drain Tubes & Fittings 5.58 ft. Cast Iron Slipper Bathtub Kit
Home Depot
Shiny Steel Toilet Brush
$10.99 | zulily
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™