How to vent a floor sink when the nearest wall is ~10' away?

[Bill Ernst]

Well, the most difficult thing about learning to plumb to code is plumbing drain, waste and vent to code. I just have never encountered an inspector who understood how to inspect the items above; distances before and after trap seal (weir), etc.
I didn’t have a question, really. Just wondered if you looked for vent fittings as they were plumbed in relation to flood plain of fixture served

 

[HForester]

The flood level rim of a fixture has nothing to do with the elevation of a trap weir nor where the trap weir is located with reference to the fitting that provides the vent for the trap. In UPC land, they do allow horizontal dry vent piping below the flood level rim of the the fixture. (IPC doesn't allow that.) In those situations, the connection of the dry vent piping to the fixture drain must be through the branch of a fitting where the branch is rolled up 45 degrees (or more) from horizontal. Typically, the branch fitting is a wye with a street 1/8 bend in the wye branch such that the axis of the inlet of the 1/8 bend is horizontal (with about the same slope as the run of the wye fitting.) This made-up combination fitting is frequently called an "upright wye and 1/8 bend" (Someone correct me if I don't have this terminology exactly right.) I have seen this (horizontal dry vent below the flood level rim) accomplished using a sanitary tee ("on its back") although some don't consider use of a san tee on its back as a proper drainage fitting. Many WCs in UPC land have been vented this way...For a WC, the trap is above the floor and therefore, the trap is above the dry vent. A DF has its trap above the floor....,

To me, a drinking fountain is such a benign application such the there isn't enough flow to ever cause the trap to self-siphon, If there are other vented fixtures connecting to the same horizontal branch drainage piping that the DF drainage pipe connects to (and usually a UPC system is "over vented"), the chances of a positive pressure event affecting that trap will be nil. So, why do you really need the vent for that trap? Does a loop vent really do anything to abate a positive pressure event?

OK, there are the purists..."gotta have a code legal vent.." So, hack the floor up to you get to a point where you can bring the dry vent pipe (a horizontal dry vent pipe below the flood level rim of the fixture) up in a wall and eventually connect it to the vent system. I don't think the UPC has a length limit for a horizontal dry vent pipe below the flood level rim of the fixture other than, "the closest place to enable turning up vertically." (Again, you UPCers correct me if I am wrong on this.) I also think that the UPC allows dry vents to be FLAT (no slope) so that shouldn't cause a long run of dry vent to eventually "rise up out of the floor."

 

[Bill Ernst]

Ok, I didn’t ask a weir flood rim question. You misunderstood. Vertically, a vent servicing a trap cannot conform to code with a combination wye and 1/8 bend due to the weir being above the vent wye...
All this other stuff is - I guess you just pontificating?

 

[georgia plans exam]

May I pontificate? 2012 I.P.C.
1. 909.1.
2. 905.3
3. 909.2 GPE

 

[HForester]

Ok, I didn’t ask a weir flood rim question. You misunderstood. Vertically, a vent servicing a trap cannot conform to code with a combination wye and 1/8 bend due to the weir being above the vent wye...

All this other stuff is - I guess you just pontificating?

You are right….I went off the rails and didn’t understand the question. In reflection, I think what your question/issue is about is whether you can have a horizontal dry vent pipe below the flood level rim of a fixture.


Someone else was correct: IPC Section 909.2 (the last part of the sentence) prohibits a horizontal dry vent pipe for a fixture trap located below the flood level rim of a fixture. However, because you stated "We have a drinking fountain in CA... " you are not working under the IPC. Under the UPC, Section 1002.4 (a 2015 edition reference) says essentially the same thing as the IPC however, the UPC (Section 905.3) also begins the section with "Unless prohibited by structural conditions...." This appears to allow for horizontal vent piping below the flood level rim of a fixture. Indeed, looking into the 2009 UPC Illustrated Training Manual (sorry I don't have a 2015 edition) under Section 905.3, it states in the second paragraph:


"The vent connection is always below the overflow rim of the fixture but normally there is only a short vertical piece that is below the fixture rim: however, this is not always possible. There will sometimes be obstructions in the structure of the building that will prevent this ideal condition. Significant portions of the vent may have to be installed below the flood-level rim of the fixture. For example, there may be an installation of a floor drain where the distance exceeds the trap to weir distance. In this installation, the vent would have to be placed in a horizontal position until it could turn vertical in the wall (see Figure 9-15)"


Figure 9-15 is a photograph showing a vent running (maybe 20 feet) horizontally below the slab where there will be a floor drain. In other words, under the UPC, apparently, if it is not possible to run the vent vertically above the flood level rim of a fixture before offsetting horizontally, it is OK to run horizontally below the flood level rim.


Now I don't agree with that practice and the UPC doesn't seem to agree with that practice (UPC Sections 1002.4 and 905.5), the "Unless prohibited by structural conditions...." of 905.3 seems to allow for horizontal dry vent piping below the flood-level rim of a fixture.

This might help you design a solution for the venting the drinking fountain.

 

[north star]

$ ~ $

HForester,

Is it possible for you provide some images of your
explanation of Post # 29 ?..........Thanks !

$ ~ $

 

[HForester]

Can anybody else put up that UPC Training Manual Figure (Figure 9-15) ? I can't do so for another week.

 

[HForester]

I added the Yellow arrow to point out that this is the dry vent pipe that will obviously be below the flood level rim of the floor drain(?) in the foreground of the figure (photo).

IMAGE available for up to 14 days from Oct 30, 2018