I've drilled 18" holes spaced at 12" along on our front porch and treated with 1/2 gallon of "Dominion 2L" solution per hole.
I was expecting the 18" (actually 12" under 6" slab) holes to continually fill and slowly soak into the dirt, but our dirt must be very porous as I could pour the solution in very quickly yet it never filled the 18" holes. I'm sure the dirt at 18 inches (12" below the 6" slab) is well saturated, but I'm wondering if the dirt above the 12" depth, up to the bottom of the slab, is still dry?
Is it possible that the solution was able to wick it's way up to the bottom of the slab, or should I backfill the holes to 1-2" below the 6" slab and re-treat each hole to ensure that all of the dirt is saturated from the bottom of the slab down to the previous 18" depth?
Note: We paid a professional to treat our underneath crawlspace area 4 years ago and a recent inspector said that still looked fine (no more termite tubes) and only recommended the sub slab treatment where I saw swarmers exiting from our window sill above the front slab. I'd pay a pro do the job, but we can't afford it at the moment so I'm attempting the treatment on my own.