help understanding code - drains

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rwn

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Having to repair my house and code enforcement says all plumbing will have to meet current code. As an engineer I can follow specifications but am unsure about the

meaning of some of the plumbing code so I want to ask these questions. I have a drawing of the current drain/vent system. Main stack is 4" cast iron and vents through roof.

1. Code section 704.3: "Connections to offsets and bases of stacks. Horizontal branches shall connect to the bases of stacks at a point located not less than 10 times the diameter of the drainage stack downstream from the stack. Except as prohibited by Section 711.2 horizontal branches shall connect to horizontal stack offsets at a point located not less than 10 times the diameter of the drainage stack downstream from the upper stack."

First thing I see is that toilet is teed to main drain about 15" above the other drain. If I understand code correctly, interval between branches must be greater than 10 times diameter of drain meaning that I need 40" between the toilet branch and another branch. Is that right?

2. The lower tee on the main stack is 2" cast iron branch draining tub, lavatory, kitchen sink, and laundry. According to table that is 7 DFU's so couldn't be drained by 2" branch. So I should change that tee to 3"?

3. Lav & kitchen sink have ptraps and vents but vents end in attic. No separate vent for tub or laundry. Main stack vents above roof.

Now to correct it.
4. Floor to ground is about 40" so I have room for only one tee to main. That one branch would have to be 3" since it includes the toilet. and 7 other dfu's. OK?

5. Assuming all ptraps are correct for size/slope/weir to drain distance, and separate vent for kitchen, laundry, lavatory, can the vents for those be joined in the attic and connected to the main stack via 3" tee ? Tub is wet-vented because trap is below floor.

8. Code section708.3.4 : "A cleanout shall be provided at the base of each waste or soil stack." I guess I need to add a cleanout at the base. Will a tee or wye above the branch tee meet that requirement? I assume it should be a 4" tee or wye with a plug. or could a double 4" tee be used at the base for branch and cleanout ? The drain goes underground at this point so a cleanout could be installed above or below the floor but not easily below branch drain. Does the code really mean that the cleanout has to be located below the lowest horizontal branch even though it is easier using it if it is above the tee or even above the floor behind a closet wall with an access panel?



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