Drain for Plumbed Washer Drip Pan

[Radio Flyer]

I’m adding an upper-level, interior laundry room. Thanks to previous guidance here, I’ve plumbed the washer drain downstream of the toilet in the adjacent bathroom, like this.

I now need to install a washer drip pan, but because of my interior-wall location and cold climate, instead of direct piping to outdoors, I’m planning to plumb the pan drain to sewer with a small 1” trap covered with mineral oil to reduce evaporation and a 1” vent.

Question: Can I connect the pan drain into the horizontal 2” washer drain underneath the floor? This would be downstream of the washer standpipe and vent, but before meeting the main 3” drain. Would the little 1” drip pan trap be protected, or would the washer drain suck it dry, despite it being downstream of the standpipe vent? (And if so, would making the pan trap larger than 1" help?)

It would look like this.

Thanks for all advice!

 

[Radio Flyer]

Any ideas on this? Hoping to plumb the drip pan today, but just want to be sure the washer drain won't suck the pan trap dry.

 

[Sponsor]

 

[Plumber01]

No. The drain line should be piped to a drain with an airgap.

I usually do something like a 2" trap with a 6x2 fitting reducer used as as funnel. Drip pan drain would terminate 1" above the funnel creating an airgap. Funnel would need a trap primer to keep the trap full.

 

[Radio Flyer]

No. The drain line should be piped to a drain with an airgap.

I usually do something like a 2" trap with a 6x2 fitting reducer used as as funnel. Drip pan drain would terminate 1" above the funnel creating an airgap. Funnel would need a trap primer to keep the trap full.

Oh, I see. So the top of the funnel (the 6" side) would be roughly at floor height and not below, right?

And the 2" drip pan trap would be okay connecting to the washer drain just downstream of it's trap?

Also, the drip pan trap and the washer trap should each have their own vents before they join at a wye, right?

Thanks again!

 

[Plumber01]

Yeah. I didn't think that through enough with the drain being at floor level.

That would work but at that point you might as well install a floor drain which is nice to have in a laundry room anyway.

Yes both would need to be properly vented and the funnel or floor drain would need trap seal protection(trap primer).