Adding a powder room to garage

[Still_Learning]

Love this forum and everyone's willingness to share their wisdom . Bought a house a couple months ago and the kitchen/laundry branch line drain had no bottom (rusted out cast iron). Since then, we've had that pipe lined with an epoxy sleeve and now have a working kitchen sink again, but before I go and repour the concrete, my better half asked about adding a powder room to our garage/workshop.

The first drawing is the current setup. Previous owners rerouted the kitchen drain into the laundry vertical to bypass the initial part of the pipe that rusted out. The second drawing is one possibility for adding a toilet and sink nearby. The third drawing is basically the same plan as the 2nd, but puts things back to the way they were initially (it likely doesn't matter, but routes a drain straight down rather than across and then down, taking up additional headspace.

Are either of the proposed acceptable plans? I'd be tying into the vent above the laundry drain in the room above the garage. Many thanks in advance for any help!

 

[wwhitney]

As long as the laundry and kitchen vents receive no drainage from above, either is fine as everything is dry vented. Dry vents need to be at least 6" above the downstream fixture flood rims before going horizontal or joining other dry vents.

Cheers, Wayne

 

[Sponsor]

 

[Still_Learning]

That's good to hear! Thanks @wwhitney! Bonus question for you or anyone else happening upon this thread:

If the wall was open and you had 60 year old copper water lines, would you:
a) leave them alone
b) replace them with PEX-A
c) replace them with new copper

 

[Reach4]

a

 

[Still_Learning]

Alright, gotta bump this again because now that I'm into it, there's not a good wall nearby where I can send the dry vent off the toilet with a vertical takeoff. If I change to the layout below, can the toilet be served using a wet vent from the sink as in the diagram below? If so, does the vent pictured heading up from the sink need to be 2" or can it be 1.5"?

 

[wwhitney]

To use the lav drain to wet vent the WC, its drain must join the WC drain before either drain joins any fixtures from the floor above.

Cheers, Wayne

 

[Jeff H Young]

move the wye or combi going to the w/c to where the green section is near where the "wet vent ?" area is.. Also Im not 100 percent of the k/S connecting to the wet vent Id tie it in downstream of wet vent to be sure