Ok, I'm getting tired of lugging laundry up and down stairs. While I appreciate the fitness of using stairs, I'm clumsy and likely to take a fall one of these days! So, I'm moving the laundry room to the 2nd floor room over garage. I'm sharing details to get a sanity check and for any other DIY person who wants to copy.

Question: Is it acceptable for new 2nd floor washdrain pipe to connect into existing laundry trap/vent in the crawl space under the house? Or do I need to trap/vent closer to the new location on 2nd floor?

Question: Can I "T" a washer drain overflow pan into the drain as designed (using current trap/vent under crawlspace), or do I need to to "trap" the overflow pan before it goes into the vertical drain from 2nd floor to crawlspace?

Question: Any other cautions or suggestions before I start? For instance, is there a problem with converting an outlet to a junction box to maintain the incoming bonus room circuit? It will be hidden behind drywall that encloses the new laundry room.

Detailed notes - PLUMBING
Install washer box between studs 3 and 4 (center of proposed laundry closet).
Install 2x4 across studs above washer box
Install 2” PVC drain between proposed washer box and existing laundry drain. Disconnect existing 2” laundry drain and tie new pipe in above existing trap. Existing trap/drain already vented to roof stack on first floor roof.
Re-route exsiting ½” hot and cold water lines from exisitng washer box to new washer box.
Install nail plate at header and sill plates to protect pipes and reinforce structural integrity
Insulate PEX supply lines.
Install vinyl flooring and washer overflow pan. Tie washer pan into 2" drain (no trap at pan since main drain is trapped under crawlspace.

Electrical:
Disconnect existing laundry circuit (110VAC and 220 VAC) at service panel.
Install new dedicated lines between service breaker panel and proposed location (12/3, 110VAC, 20A) + (10/3, 220VAC, 30A).
Convert 110VAC plug into junction box to maintain bonus room circuit (cannot have other outlets located in proposed laundry closet location).

Other:
Install dryer vent direct through external wall. Vent exhaust shall be at least 18” or more above 1st floor shingle roof.
Install vented folding closet doors to ensure proper ventilation
Install washer with braided hoses
Install electric dryer and connect to exhaust vent.

That's it... comments, suggestions, and questions requested. Thanks! Aaron

Nice CAD's. I would lay this job out a little differently. I would cap off the old washer drain and trap at the main. I would then 45 the existing laundry roof vent over to where I wished to install the new washer box. You could pick up the washer trap and stand pipe off the vent stack which would then become a stack vent from that point down. Continuing up from the tee through the ceiling to the attic where you can then offset back to the point where it exits the attic out the roof. This cuts out a extra pipe and gets away from a two story drop to the trap when the washer discharges. Sound like a plan? Regards, Tom