amadogon49
Jan 18, 2011, 07:56 AM
Hello I live in Northern New Jersey and my town follows the 2009 National Standard Plumbing code from the PHCC which is what my town follows:
So they have this snippiet of verbose code:
12.8 FIXTURE VENTS
12.8.1 Venting of Fixture Drains
Fixture drains shall have a vent so located that the vent connects above the top weir of the trap and the developed
length of the trap arm is within the limits set forth in Table 12.8.1.
EXCEPTIONS:
(1) Water closets and similar siphonic fixtures.
(2) Combination waste and vent systems. (see Section 12.17)
(3) Vents may be connected below the top weir of the fixture trap if the following conditions are met:
a) The vertical section of the drain pipe shall be at least one pipe size larger than the trap inlet size.
b) The horizontal pipe connected to the trap outlet shall be at least two pipe diameters long.
c) The developed length of the trap arm shall not exceed the values in Table 12.8.1.
Table 12.8.1
MAXIMUM LENGTH OF TRAP ARM
Size of Trap Arm (Inches) Length – Trap Arm to Vent Slope – Inches per Foot
1- 1/4 - 3' 6" - 1/4
1-1/2 - 5' - 1/4
2 - 8' - 1/4
3 - 10' - 1/8
4 - 12' - 1/8
NOTES FOR TABLE 12.8.1:
This table has been expanded in the "length" requirements to reflect expanded application of the wet venting
principles. Slope shall not exceed 1/4" per foot.
12.12 FIXTURE REVENTING
12.12.2 Horizontal Branches
Three lavatories or one sink within 8 feet developed length of a main vented line my be installed on a 2" horizontal
waste branch without reventing, provided the branch is not less than 2 inches in diameter throughout it's length
and provided the wastes are connected into the side of the branch and the branch leads to its stack connection with a
grade of not more than 1/4 inch per foot. [/B]
So, the first section where it talks about the vent being above/below the trap weir. If I do indeed increase the size of the drain by 1 pipe size than the trap itself, does this mean I can connect the vent to the drain below the floor using a wye as long as I follow the maximum thresholds of 8' developed length and 1/4 inch per foot pitch?
In addition if the above assmption is true, I would envision at least a small trap arm size before it goes vertical, since if you didn't have a horizontal trap arm, the trap would turn into an s-trap, no?
A couple of weeks back you guys helped me out deciding on a kitchen revent design if you remember, and in that thread I could have done two things:
1) Use a wet vent as long as it was one pipe larger than the trap and within 8' feet of a stack.
2) Or, Build out a secondary vent stack that was less than 5 feet away, at that point the vent would be 1 1/2" and the drain 2". THe only problem I had with this solution, was my concern with boring through several 2x4's since this plumbing was being done on a load bearing exterior wall over a window. Eventually I figured I put the trap arm flush with the studs instead of boring through them and offset the back of the kitchen cabinetry to make it all fit.
But if I can connect the vent underneath the floor with the drain, this would make this a whole lot easier since I would have to concern myself with a trap arm going through studs at all.
Thank You,
Amado
So they have this snippiet of verbose code:
12.8 FIXTURE VENTS
12.8.1 Venting of Fixture Drains
Fixture drains shall have a vent so located that the vent connects above the top weir of the trap and the developed
length of the trap arm is within the limits set forth in Table 12.8.1.
EXCEPTIONS:
(1) Water closets and similar siphonic fixtures.
(2) Combination waste and vent systems. (see Section 12.17)
(3) Vents may be connected below the top weir of the fixture trap if the following conditions are met:
a) The vertical section of the drain pipe shall be at least one pipe size larger than the trap inlet size.
b) The horizontal pipe connected to the trap outlet shall be at least two pipe diameters long.
c) The developed length of the trap arm shall not exceed the values in Table 12.8.1.
Table 12.8.1
MAXIMUM LENGTH OF TRAP ARM
Size of Trap Arm (Inches) Length – Trap Arm to Vent Slope – Inches per Foot
1- 1/4 - 3' 6" - 1/4
1-1/2 - 5' - 1/4
2 - 8' - 1/4
3 - 10' - 1/8
4 - 12' - 1/8
NOTES FOR TABLE 12.8.1:
This table has been expanded in the "length" requirements to reflect expanded application of the wet venting
principles. Slope shall not exceed 1/4" per foot.
12.12 FIXTURE REVENTING
12.12.2 Horizontal Branches
Three lavatories or one sink within 8 feet developed length of a main vented line my be installed on a 2" horizontal
waste branch without reventing, provided the branch is not less than 2 inches in diameter throughout it's length
and provided the wastes are connected into the side of the branch and the branch leads to its stack connection with a
grade of not more than 1/4 inch per foot. [/B]
So, the first section where it talks about the vent being above/below the trap weir. If I do indeed increase the size of the drain by 1 pipe size than the trap itself, does this mean I can connect the vent to the drain below the floor using a wye as long as I follow the maximum thresholds of 8' developed length and 1/4 inch per foot pitch?
In addition if the above assmption is true, I would envision at least a small trap arm size before it goes vertical, since if you didn't have a horizontal trap arm, the trap would turn into an s-trap, no?
A couple of weeks back you guys helped me out deciding on a kitchen revent design if you remember, and in that thread I could have done two things:
1) Use a wet vent as long as it was one pipe larger than the trap and within 8' feet of a stack.
2) Or, Build out a secondary vent stack that was less than 5 feet away, at that point the vent would be 1 1/2" and the drain 2". THe only problem I had with this solution, was my concern with boring through several 2x4's since this plumbing was being done on a load bearing exterior wall over a window. Eventually I figured I put the trap arm flush with the studs instead of boring through them and offset the back of the kitchen cabinetry to make it all fit.
But if I can connect the vent underneath the floor with the drain, this would make this a whole lot easier since I would have to concern myself with a trap arm going through studs at all.
Thank You,
Amado