Planning slab penetrations for a basement bathroom

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Jay S

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I'm planning new construction, my questions involve a basement bathroom w/ a tub, shower, wc & vanity as shown.

First 2 general code / best practices questions which reveal my level of experience...
1) Since 3" or larger pipes are called for under slabs, does that mean traps under basement slabs for tubs/showers need to be 3", or are 2" traps allowed?

2) Can a hvac condensate drain and or a water heater overflow/drain pan be fed into the septic, or should I put in a separate daylight drain line for those things?

Questions about my basement bathroom drawing:
Are the basement fixtures properly vented? 1) Are they wet /horizontally vented to the stack pipe OK? 2) Is the stack pipe an acceptable vent? (This pipe comes down from the 3rd floor, where it drains a vanity, wc and tub/shwr on that floor, and it continues up with a 2" pipe out the roof.)

If the basement fixtures are properly vented as drawn, can I use any 3" under the slab and 3" the vertical stack (or must it all be 4")? (I have read different things about the maximum trap arm lengths of wet venting 3" and 4" pipe???). The pipe under the slab will be sloped slightly more than 1/8" per ft.

If this is not acceptable venting of the basement bath, any advice on a good approach to proper venting would be appreciated, I need to get any extra slab penetrations required for proper venting before we pour....

THANKS! -jay

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