Venting of new construction

**TheEplumber** · 02-02-2012, 08:27 PM

Quote:

Originally Posted by Javiles

Again the reason for this rule is the venturi principle for plumbing.. plumbing design 101
If you increase the size of the vent over the soil service line, you can end up with auto siphon action, this would happen on windy days, the air rushing over the vent creates a vacuum in the system this would cause this action and could pull the traps dry. This is why you cannot go over.

So, you're saying I can't use a 4x4x6 combo to vent my building drain?

Javiles · 02-02-2012, 08:38 PM

Quote:

Originally Posted by TheEplumber

So, you're saying I can't use a 4x4x6 combo to vent my building drain?

If you’re venting off the 6 you can’t go 8 if off the 4 you can’t go six that you cannot vent 6 on 4 soil at least not under our code. I took a course in plumbing systems design before I took my masters and this was one of the issues covered in the venting portion.

Lyndon · 02-02-2012, 08:58 PM

Therefore, it seems to me you are saying that I should only have a maximum of one 4" vent out the roof in my situation. Is this correct? Anything larger would be just asking for problems?

**TheEplumber** · 02-02-2012, 08:58 PM

Quote:

Originally Posted by Javiles

If you’re venting off the 6 you can’t go 8 if off the 4 you can’t go six that you cannot vent 6 on 4 soil at least not under our code. I took a course in plumbing systems design before I took my masters and this was one of the issues covered in the venting portion.

Can i go 5" on 4"? (only kidding) Seriously though, I'm trying to see how a plumber would oversize a vent like this-or why.
BTW, i don't recall anything like this in the UPC. I don't think it's covered but I may be wrong

Lyndon · 02-02-2012, 09:31 PM

Javiles,

Thanks for a very intelligent answer. So let me just make sure. I should not vent a 4" sewer line with two 4" vents at the opposite ends of the line or I will be just asking for problems. Correct?

Plumber101 · 02-02-2012, 10:08 PM

Quote:

Originally Posted by Lyndon

Javiles,

Thanks for a very intelligent answer. So let me just make sure. I should not vent a 4" sewer line with two 4" vents at the opposite ends of the line or I will be just asking for problems. Correct?

You can vent 4" at both ends and should since you will be tieing in several vents and the 4" will be the header

Lyndon · 02-06-2012, 01:52 PM

Okay, let me see if I finally understand these two rules. These two sections of the code are independent of each other?

1) Drainage piping shall be vented by means of one or more vent pipes, the aggregate cross-section area of which shall not be less than that of the largest required building sewer.

Therefore, if the main (largest) required waste line is 4", I could install two 4" vents through the roof which would equal double the cross-section area of the largest waste line. Since the code requires the aggregate cross-section area to NOT BE LESS than that of the largest required building sewer, this setup would meet the qualifications of this rule?

2) The diameter of a vent stack cannot exceed the diameter of the waste line to which it connects.

Again, since each of the two 4" roof penetration vents are not larger than that of the largest 4" building sewer, this setup would meet the qualifications of this rule?

Therefore, it is entirely within code to exit the roof with two 4" vents even though the maximum sewer line is only 4"?