On Oct 6, 12:03*pm, tim birr wrote:
I don't think there is anything to try, other than digging.

Since the water from the problem pipe is not "bubbling" back up and
spilling out over the top of the concrete slab, that indicates to me
that here is not a major block, but rather a hole just below the slab.

I posted some photos of the set-up on flickr. You can see them hehttp://www.flickr.com/photos/68323376@N05/

Hope you can see that there is nothing to prevent "backflow" from
coming up back over the slab. *All the other drains are running
fine....so....makes sense there is a hole just below the slab.

I took today and Friday off (West Coast), rain is set to return on
Saturday, so I had better go start digging to see what I see, but any
thoughts, welcome.

It looks like in the pictures that there is a metal reducer that goes
from the gutters down to the PVC in the slab. I would unscrew that
first and see if you can remove it. Then run a waterhose (or a small
pipe camera) to see if there actually is a hole.

Robin