There's a concrete slab at the base of the stairs out the back door that goes into the driveway some and then oak tree roots themselves make it a little bumpy ride.

When they sign, they are responsible for clogs unless it's clogged by tree roots or some other condition out of their control. 

We have roots in Whidbey Island and I am committed to Real Estate Investment in the area.

I pull the carpet/pad and tack strip, use a  bleach water solution to mop subfloor  (with respirator) rinse,  then after dry, I also use the oil based kilz on subfloor (pretty thick, respirator a must); then, and I am rooting for you Jeff, and hoping you do not need the next step..... but if you still smell it.....

I'll be rooting for you to get the sales price you need to deem this one a big success for you guys. 

I went to Clover Park high school in Lakewood (Pierce County) and WSU and actually root for UW when they aren't playing my Cougs. 

In 2015 I've tried to "get back to my roots" of investing.

I think it's been at least a few months since the BBQ place shut down.Your second question is spot on, and is the root of the reason for my post.  

Is it clogged because of tree roots?

You answered the root of my question - - - I'm very interested in other investors' criteria.