Avoiding a Horizontal Vent

quinocampa

quinocampa

Mechanical engineer in marketing. Uhuh.
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Avoiding a horizontal vent is discussed here regularly, but I do not see how it can be avoided when your vent and drain are going in opposite directions between joists. The vent needs to clear a joist to get behind the wall, and the drain has to clear a joist on the other side and move in the other direction. Surely this is a common situation. What is the common solution?

Thank you!
 

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drain

NO way to tell without seeing the entire situation to determine if there is a better way. You are only considering one possibility. A plumber would look at all possibilities then do the best one.
 
It is not that you can not use horizontal venting there is just a limit on how far you can run it. Here is the part of the Illinois plumbing code. The part in bold and underlined is about the horizontal venting. But the whole code is important about vent sizing.

Section 890.1580 Size and Length of Vents



a) Size of Water Closet Vents. A water closet shall have at least a 2 inch vent.

b) Size of Individual Vents. The diameter of an individual vent shall be at least 1¼ inches or at least ½ the diameter of the drain to which it connects, whichever is greater.

c) Size of Relief Vents. The diameter of a relief vent shall be at least ½ the diameter of the soil or waste branch to which it is connected.

d) Size of Circuit Vents. The diameter of a circuit vent shall be at least ½ the diameter of the horizontal soil or waste branch or the diameter of the vent stack, whichever is smaller. (See Appendix A: Table L.)

e) Size of Vent Piping. The size of vent piping shall be determined based upon its length and the total number of drainage fixture units connected thereto as provided in Appendix A: Table K. No more than 20 percent of the maximum developed length as determined from Table K may be installed in the horizontal position. Vent piping serving floor drains shall be installed in such a manner as to minimize horizontal vent distances.​
 
Well, the horizontal distance is like 12 inches! And the vent would be 2", and it would serve only the toilet. Downstream, I want to feed the 2" shower drain into the toilet's 3" drain, which will run about 7 ft to the main drain line. The shower will have its own vent before it joins the 3" toilet arm.
 
horizontal

The problem with that citation is that it refers to overhead horizontal vents, not one below the overflow line of the fixture, or under the floor as this one would be. Where an underfloor "wetable" vent is concerned it has specific requirements, and might require consultation with an inspector as to what he will accept before installing it.
 
Sometimes to catch your vent you can not always run direct.Here, you have up to 4' to make your vent connection.So the term "shoot" hook is what we use.(Think u turn)
 
SewerRatz said:
It is not that you can not use horizontal venting there is just a limit on how far you can run it. Here is the part of the Illinois plumbing code. The part in bold and underlined is about the horizontal venting. But the whole code is important about vent sizing.

Section 890.1580 Size and Length of Vents



...(snip)...

b) Size of Individual Vents. The diameter of an individual vent shall be at least 1¼ inches or at least ½ the diameter of the drain to which it connects, whichever is greater.

... (snip)...

e) Size of Vent Piping. The size of vent piping shall be determined based upon its length and the total number of drainage fixture units connected thereto as provided in Appendix A: Table K. No more than 20 percent of the maximum developed length as determined from Table K may be installed in the horizontal position. Vent piping serving floor drains shall be installed in such a manner as to minimize horizontal vent distances.​
Click to expand...

So according to b), I need only an 1-1/4" for a 2" shower drain. Now, Massey quotes the UPC, saying "When the vent diameter is increased one pipe size for its entire length, the maximum length limitation does not apply." (p41 Plumber's Handbook, Designing Vent Systems) I'd like to run a 2" vent and join it with the toilet's 2" vent before heading over to the 3" main vent.
Also, "The horizontal section of a vent pipe must not exceed 1/3 of the total permitted length of vent pipe."
Now, his 1/3 contradicts the 20% listed above. Also, is that 20% or 1/3 of what you've actually run, or is that of the total PERMITTED length, which in his table is 150 ft for a 2" vent. You see, once I get into my attic, I have to run about 9 ft to catch the main vent. Since it is February and I have a steep pitch on my roof, I am loathe to put in a separate vent.
 
I have never in 36 years, had to nor have I ever run a horizontal vent below the flood level rim for any fixture and or drain. There is always a way.
 
Hey, I completely agree with you! And I do not intend to. I have mentally resolved that issue by considering other options. However, now I realize that the vent above will have to run horizontal to meet the main vent, and that distance is suspect until I can get a clear interpretation of the code. Basically, the vent will be horizontal about 9 ft above the floor and run horizontal for about 9 ft to the main vent. If I can do that, great. If not, I have to just go vertical thru the roof, which is challenging (February, steep roof...)
 
vent

1. I have NEVER met an inspector who limited the distance or amount of horizontal dry vent piping.
2. good luck finding ANY 1 1/4" anything, pipe or fittings, for your shower vent.
 
hj said:
1. I have NEVER met an inspector who limited the distance or amount of horizontal dry vent piping.
2. good luck finding ANY 1 1/4" anything, pipe or fittings, for your shower vent.
Click to expand...

HJ, I have better than a thousand feet of 1 1/4 sch 40 pvc on the rack that was donated years ago. Unfortunatly I don't have one single fitting for it. We occasionally use it for rollers or the drama club will take it to make stuff.
 
Well that is what our code book says. Personly we basicly do everyting here in 2" and 4" drains and vents. It is simpler and less fittings. As for how long a dry vent can be ran horzontail our code limits it.
 
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pipe

1 1/4" PVC, as long as it is not DWV, and pressure fittings, are a common item, but not for use in drainage, and drain fittings are usually only a special order item. 1 1/4" ABS is a hopeless cause.
 
hj said:
NO way to tell without seeing the entire situation to determine if there is a better way. You are only considering one possibility. A plumber would look at all possibilities then do the best one.
Click to expand...

Okay HJ, this one was designed with you in mind!
I have two options I am considering for my toilet drain and vent. One has a short horizontal run and the other has a 180 bend. The 180 bend eliminates the horizontal run, at the expense of several inches of drop that could be better used to accelerate the drain to the main vent. Also, might the bend be too tight, restricting flow? Please choose the ideal option.

And as an aside, my shower vent will be 1-1/2 (not 1-1/4 -- "unobtanium") and the toilet vent is 2".
Also, I'm aware I didn't show a reducer from the 3" to 2" vent on one of my sketches (without the low heel).
Thanks!!
 

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drain

The problem is that you are limiting me to YOUR ideas of how it could be done. If I could see the big picture, I might want to put the vent across the room at a different wall so the flow goes from the toilet to the combination Y-1/8 bend vent and then to the main drain. But since I cannot see the rest of construction, I do not know if that is a viable option.
 
hj said:
The problem is that you are limiting me to YOUR ideas of how it could be done. If I could see the big picture, I might want to put the vent across the room at a different wall so the flow goes from the toilet to the combination Y-1/8 bend vent and then to the main drain. But since I cannot see the rest of construction, I do not know if that is a viable option.
Click to expand...

That is a fair statement based on what I've posted. The nearest wall is the one up through which the vent is shown running. There is another wall perpendicular to that, 15" off toilet's centerline. I plan it to have a large glass block "window" and therefore a vent can only run to either side of the glass blocks. I'd end up with at least several inches of horizontal vent below flood line to get there, and still have to turn another 90deg toward the main trunk. Next closer walls have two 3/4" supply lines running horizontal -- no room for a vertical 2" vent. No other walls are in the vent-within-5ft restriction for a 3" drain. If I ran straight to the main trunk with no vent, it is about 7' away, longer if you measure from the toilet trap above floor level to the vent orifice in the crawlspace. I can post a floor plan when I get home tonight.
 
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Bathroom Layout

Here is the layout I described. As you can see, there is a wall behind and beside the toilet. If you're sitting on the toilet, the corner in front of you on the left has water supply lines running in both directions, blocking a vent from going up. The main vent is straight ahead. Other walls are too far away, so I chose the wall behind. Of course, I still have that wall to build yet...heh...
 

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One Last Request

Okay, I intend to work on the plumbing this weekend, as I have the entire rest of the project ahead of me. I know that both of my sketches above will work. They're vented within the right distance, no s-traps, even the horizontal vent is short enough to qualify under code. I can't wring my hands for weeks about the PERFECT solution. The reasons I gave about wall locations pretty much leave me with the two options I sketched. If the 180 degree bend is not too restrictive (is isn't more than the toilet's own S-trap!), then it's my first choice. Objections? Final answer?
 
were in similar situations :)

my thread is " Sanitary Tee on its back... "

im thinking of doing a long U-turn...
 
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