Washer Waste Drain Slope

[suzyq2626]

I am currently trying to install a washer and dryer into a room off the side of my house, with an outdoor crawlspace (no walls, just 2 pillars), therefore the floor joists under this room are exposed to the elements. I am trying to connect the new waste drain to an existing drain that runs under the existing house perpendicular to this new one. Therefore, I could just meet this exist. drain with a tee, BUT the height of this drain at the point I would connect them is HIGHER than the height of the new drain; therefore creating a negative slope on the new drain pipe. How do I get the drain to slope positively? Any ideas? (I hope this was easy to visualize...)

 

[Gary Swart]

The only way to make what you have described work, is to make the washer end of the drain higher than the existing drain. You didn't say how much elevation you need to get gain to get a 1/4" per foot slope or what size the joists are, but if the elevation you need to gain isn't too much and the joists are like 2x10s or 2x12s, you can notch the floor joists enough to fit the drain pipe then bolt sister 2xs on each side of the joist to strengthen them.