Double Lavatory Conversion

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Paul E.

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Hey ya'll, I'm trying to correctly plumb in a double lavatory setup, where a single lavatory was. The plan is to tie into the 2" cast iron pipe and continue the vent upwards through the existing roof penetration. I am showing a double fixture tee, as reading other threads, it seems a double sanitary tee is not appropriate.

Do I need a test tee as shown? This has to pass inspection with the city, so I think I have to pass a water test with a 5-foot head for 15 minutes. The plan would be to add an inflatable plug and cap the trap arms. Then fill from the roof.
 

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Sylvan

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30" from the vent seems a bit too much

Normally we install a trap and the vent shall be 24" from the trap and the trap can be 24" away from the fixture being served

Check your local code as we normally test with a 10 foot head of water which equals 4.34 pounds pressure
 

wwhitney

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So, if the old lav tied into the 3" line (as it appears), what's the 2" line? If it's a dry vent for a fixture on a lower level, you can't add drainage to it.

As for the test tee, whether it's required for testing or not, it's a good idea to have it as a cleanout. Since I understand snaking through a double fixture fitting and coming out the bottom rather than skipping across is hard to do.

Cheers, Wayne
 

Paul E.

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Here's a photo of the original venting, the lav in the master bath tied into the 2" line, the hallway lav tied into the 3" line. I don't really know why there are two vents so close, but I guess that's how they did it back in 1969? This is a single story house, so no fixtures below, just Texas clay underneath the slab.

Original Layout.jpg


Floor Plan.png


And a bonus photo of the original copper drain line (rotated 180 degrees in the image) for the hallway lavatory that connected into the 3" cast iron pipe. I don't think any waste water was making it to the sewer.

Copper Pipe.jpg


So the lavatory needs to be within 24" of the p trap, which needs to be within 24" of the vent? Could I move the p trap 6" closer to the vent then?
 

wwhitney

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Thanks for clarifying there are no fixtures in the story below. : - )

As to the lav trap arm length, it is measured from the trap outlet (under the sink) to the double fixture fitting. So both the portion in the wall or outside the wall.

IPC or UPC in your location? IPC allows a 1.5" trap arm to be up to 6' long. UPC allows up to 42". In both cases the trap arm can fall no more than one pipe diameter (1.5"), so it has to be horizontal, and at exactly 1/4" per foot to achieve the IPC maximum of 6' in length.

Cheers, Wayne
 

Mr tee

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Listen to Wayne, although if they do not require a test I wouldn't bother with the clean-out - I can't imagine a 3" line getting clogged by a couple of lavs. A clean-out wouldn't hurt anything, but I can't picture you ever using it.
 

Paul E.

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Appreciate all the help so far. It looks like I am subject to UPC 2021 - so my trap arm is limited to 42" then.

Fixture Trap Distances.JPG


My city does show I'll need to pass a water test. Am I understanding it correctly that trap arms are included in that test? So I would need to locate that cleanout between the cast iron pipe and the double fixture fitting?

Plumbing Top Out.JPG
 

Mr tee

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Talk to the inspector, he may waive the test on such a small change.
 

Paul E.

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So it turns out the double fixture fitting and a medium 90 wouldn't quite let me position sink #2 where it needed to go. It lands 3" to the right of the 2" cast iron line, so I've plumbed it over to the 3" line instead. Feedback is appreciated!

mo1ukJU.jpg
 

wwhitney

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The UPC does not allow the trap arms of sink 1 and sink 2 to be combined prior to venting.

From the Elevation looks like you have space for stacked san-tees on the 2" stack. If you replace the 2x1-1/2 "reducer" just above the 2x1-1/2x2 san-tee with a (possibly street) 2x1-1/2x1-1/2 san-tee, then sink 2 could hit the new san-tee. The 2" pipe between the two san-tee is an acceptable vertical wet vent.

Or if you prefer, you could rework the connectivity on the 3" stack in a couple different ways to make it compliant.

Also, not sure if a quarter bend is really allowed by the UPC in a 1-1/2" lav trap arm, but I understand it's a fairly common practice.

Lastly, not sure if I ever asked about what the 2" and 3" drains do once they enter the slab. If the 2" drain goes on to hit a WC and is wet venting that WC, then under the UPC it needs a 2" vent, not a 1-1/2" vent.

Cheers, Wayne
 

Paul E.

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Thank you for the ongoing help!

Is this sketch depicting what you're describing in the stacked sanitary tee option off the 2" cast iron pipe?
DRyCVEW.jpg


And is this an acceptable way to incorporate a vent if sinks 1 and 2 are tied into the 3" cast iron line? (Sorry the elevation started running into the plan, I ran out of room!)
uvr4065.jpg


I don't believe the 2" picks up a WC, I think it connects directly to the main 4" drain line. The existing vent for it was 1-1/2" galvanized pipe. I believe the 3" line acts as the vent for the two toilets and two showers that are adjacent to it. Here's a floor plan showing the existing fixtures, and my best guess on how they are connected together. Might be time to go buy a borescope. :)
IjNSlFg.jpg
 

wwhitney

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On the first drawing, yes.

On the second drawing, almost. The UPC requires that the upright combo that is your dry vent takeoff be a 2 x 1-1/2 x 1-1/2 combo, because the minimum wet vent size is 2". And then of course that 2" would extend to the san-tee. [If both lavs were dry vented before they combined on the horizontal with a combo, that combo would still need a 2" outlet, as a horizontal 1-1/2" drain is limited by the UPC to 1 DFU.] [Also, if the double lavs weren't wet venting anything else downstream (but they probably are), then the 2" vertical stack between the two san-tees could be omitted.]

As to underslab wet venting, if you're definitely under the UPC, then it limits horizontal wet venting to a single bathroom at a time. So each WC would need to be on a separate 3" (or 4") branch. I.e. branch A would be lav - tub - WC, branch B would be lav - tub - WC, and only then would branch A or branch B join each other or anything upstream. And then the 2" CIP would need to maintain a 2" vent through the roof (but could revent to your 3" vent).

While if you are perhaps on the IPC, the above blue layout would be fine (but likely you wouldn't really have that 4 way junction, the upper tub would go straight across to hit the 4" line between the wall and the WC). Of course, if you are/were on the IPC. alot of my previous answers would change, too (to be more lenient).

Cheers, Wayne
 

Paul E.

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Wayne, I appreciate all your insight and help so far! In the end, I was able to use the double fixture fitting, and avoid some of the complications of the alternative options. Here's a photo of the rough plumbing. Please let me know if you see anything that should be done differently, I am subject to UPC.

I believe it's acceptable to combine the 1.5" vent into the 2" vent, as the 2" vent should support 24 DFUs, and the two bathrooms account for 16 DFUs. The center of the vent elbow is at 44", which puts me above the flood rim of the bathroom vanity. All horizontal runs are sloped at 1/4" per foot.

94g6zha.jpg
 

wwhitney

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Looks OK to me. My only question is whether the 3" cast iron line should have a 3" cleanout.

Cheers, Wayne
 

Paul E.

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That's a good question, Wayne. I guess my thinking was the cleanouts were primarily added to facilitate the water test. But I see how it makes sense for the 3" cast iron to have a 3" cleanout, and then adapt down to 2". Is what I'm showing a code violation, or fall more towards up to the discretion of the inspector?
 

John Gayewski

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A3"pipe must have a3"cleanout (which actually measures 2.5"and is referenced as such in the code) so yes its a violation, but still in reality the inspector does have discretion although they aren't supposed to.
 

Jeff H Young

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a 3 inch line wouldnt require a clean out if it was a short branch off the main and the main had a cleanout upstream .
but I think thats the end of line so john is right its need one (3 inch technicaly 2 1/2inch not 2 ) to meet code.
If it was all new work Id put a cleanout 3 inch for sure.
But it looks built already looks good I think its fine and youll pass. Let us know Id like to know if he nit picks or not good luck!
 

John Gayewski

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a 3 inch line wouldnt require a clean out if it was a short branch off the main and the main had a cleanout upstream .
but I think thats the end of line so john is right its need one (3 inch technicaly 2 1/2inch not 2 ) to meet code.
If it was all new work Id put a cleanout 3 inch for sure.
But it looks built already looks good I think its fine and youll pass. Let us know Id like to know if he nit picks or not good luck!
The question wasn't whether one was required in that situation. It was whether a 3" cleanout can have a 2" access point.

So if your going to put a clean out in, it needs to be the proper size regardless of where a cleanout is required.
 

Jeff H Young

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The question wasn't whether one was required in that situation. It was whether a 3" cleanout can have a 2" access point.

So if your going to put a clean out in, it needs to be the proper size regardless of where a cleanout is required.
If no clean out is required there is no problem or code preventing a 2 inch test tee thats totally acceptable to install.
 

John Gayewski

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If no clean out is required there is no problem or code preventing a 2 inch test tee thats totally acceptable to install.
Then you bury it in the wall with no access as you can't pull a 3" plug through a 1.5" hole. It's no longer a cleanout.
 
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