Washer Standpipe Redo

[Jeff167234]

I'm looking to fix an issue with my washer standpipe as well as upgrade from 1 1/2" to 2".
Currently my Humidifier condensate drain is incorrectly directly connected to the standpipe. I will be fixing that with an air gaped connection.

However my question is about upgrading to a 2" standpipe. Current 1 1/2" standpipe transitions to a 2" drain after the san tee with a 1 1/2" vent.

My plan would be to redo the standpipe with 2", using a 2" ptrap into a 2 x 1 1/2 x 2 san tee down to the 2" drain. I also plan on installing a proper outlet box.

Im going to raise the P Trap up so I can get into that stud bay to connect to the outlet box. I will be within the 18-30" range for the standpipe so I think raising the trap is ok.

Also not sure why they used that coupler on the 2" drain, should I replace that with a glued ABS coupler?

 

[qlopp]

I'm not a plumber and have a standpipe related question on this forum, so I'm just replying with food for thought, not pro advice.

Per UPC code which seems more restrictive than IPC and goes into more detail, the trap weir must be 6" - 18" above finished floor. The weir is the point in the trap where no more water can stand before it flows out the arm, so the weir line is approximately a horizontal plane which includes the bottom of the trap arm. If you can keep this below 18" and then keep the rest of the standpipe's length between 18" and 30" you're good. The total height should be higher than the flood rim of any connected fixture (washing machine or sink).

RE: coupler, presuming this refers to the shielded flexible coupler near the floor, a solvent weld coupler would be better but maybe the original installation was done to allow easy removal for snaking? Of course a cleanout is the normal/correct way, so this gives you the opportunity to install a cleanout Tee near the floor. Also, are you sure there isn't an old trap below grade? You can snake or camera it to feel/look for a trap. That would be bad if there was.

 

[Sponsor]

 

[Jeff167234]

Thanks for the info. I have no idea why they use that flexible coupler. I could install a clean out T with this upgrade. I have no idea what is below that pipe, I assume it goes into my sewer main. A little ways to the left in that photo is the main pipe for the toilets with a clean out, the sewer main runs to the right of the photo out the house. This has all been in place for 50 years. The humidifier drain is incorrectly connected to the stand pipe and will not pass an inspection when I need to replace my furnace in the future. I inherited this 23 years ago and have just left it alone. Now its time to correct it.

I'm leaning towards removing that flexible coupler replacing with a glued coupler, then raise the trap to the 6" - 18" above the "finished floor". I wonder if they consider the finished floor the crawl space floor or the washer room floor. The first photo shows the footer for the washer room wall, and I plan on putting the P trap in that stud bay, then using a trap arm to get back to the san tee which I will raise up...

 

[Tuttles Revenge]

Looks pretty straight forward. The top of the concrete footing is at or near the floor level of the clothes washer? That floor level would be the point where the measurement is taken to get the 6-18".. and build the standpipe up no higher than 30" from there. The No Hub band is technically not allowed, but since it connects 2 equal diameter pipes its often overlooked. An ABS coupling, or cleanout fitting could be used there as well. A cleanout is required on a laundry in UPC code so I like to install them above the clothes washer so that its easily accessible and you could run water down the drain if you do end up snaking it.