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I am installing a drain pipe for my washing machine. The pipe will be going outside to a dry well. I will be using 2 inch pvc with a trap on the bottom exiting the wall of my house about 4 feet under the ground level and then piped to a buried drywell. My question is after the pipe goes through the wall to the outside, do I have to install a vent pipe going directly up to the surface; or is no venting necessary. I'm not sure how this works.
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While there are dozens of plumbing codes primarily they are all based upon either the Uniform Plumbing Code (UPC) or the International Residential Code (IRC).
In order to properly answer your question I would need to know what plumbing code is in effect in your jurisdiction because the UPC and the IRC take some dramatically different views on venting.
UNDER THE INTERNATIONAL RESIDENTIAL CODE:
1. All structure MUST HAVE a minimum of one MAIN VENT that runs undiminished in size from the building MAIN DRAIN through the roof.
2. Additional auxillary vents may be reduced to 1/2 the diameter of the pipe served once they are 6" above the flood level rim of the highest fixture served, but in no case may a vent line be less that 1-1/4".
3. The maximum developed length of a waste arm when measured along the top of the pipe from the trap weir to the vent opening shall not exceed the diameter of the pipe divided by the required pitch. (All horizontal lines equal to or less than 3" require 1/4" per ft. pitch) I.E. A 2" diameter line would equal 2" / .25" = 8ft.
4.The minimum length of a Waste arm shall be equal to 2 times the pipe diameter.
5. The minimum height of a laundry standpipe SHALL BE 18" when measured from the trap input opening to the top of the standpipe.
6.The maximum height of a laundry standpipe SHALL BE 42" when measured from the trap input opening to the top of the standpipe.
7. The trap may be installed below the floor.
8. The vent may terminate a. through the roof, b.in the Attic space (not a good practice), and c,Through the wall (must meet a number of additional specifications), d.by means of an Air Admittance Vavle (commonly called an AAV, cheater vent or Studor vent).
9. Vent lines may be horizontal once they are 6" above the flood level rim of the highest fixture served.
10. All horizontal and vertical dry vents must be constructed with DWV fittings and must be pitched back toward the drain.
UNDER THE UNIFORM PLUMBING CODE.
1. All required vents must be sized by DFU load.
2.The combined aggregate of all vents must be equal to or greater than the DFU load of the building Main Drain.
3. ALL vents MUST TERMINATE through the roof.
4. Horizontal offsets may be no flatter than 45deg from vertical.
5. The maximum developed length of a waste arm may not exceed the specifications in table UPC-T10-1
1-1/4" = 2' 6"
1-1/2" = 3' 6"
2" = 5'
3" = 6'
4" =10'
6.The minimum length of a waste arm Must be 2 times the pipe diameter.
7. Only one Air Admittance Valve permitted per structure and it requires the written approval of the local AHJ( authority having jurisdiction.)
(img)http://www.homerepairforum.com/images/uploads/2005-11-24_UPC_laundry_standpipe_w550.JPG(/img)
GENERAL RULES COMMON TO ALL CODES:
In regions subject to frost all vents MUST BE increased to 3" diameter at least one foot inside the structure before penetrating the roof.
No vents on the outside of the structure in areas subject to frost.
All Pipes passing through a masonary wall must be sleeved. To make a sleeve you first install a pipe at least 2 nominal trade sizes larger than the desired pipe through the masonary and extending out 2" on either side. The sleeve may be sealed to the masonary by any suitable means. The space between the inside of the sleeve and the outside of the desired pipe must be sealed by means of expansion foam.
All horizontal lines equal to or less than 3" must have a 1/4" per foot pitch dropping in the down stream direction.
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