Plumbing and Piping - Basement Floor Drainage Question

My washer drains into a utility tub, which runs into a verticle pipe and into the floor. There is a floor drain under the tub also, when the tub water drains out fast, the floor drain will rise and sometimes backup into the floor. No other drain in the house causes the basement floor drain to backup like this, only the utility tub. I recently used a wooden stick to push down the floor drain to see if I could move anything around or if there were any clogs. When I push the stick down it feels like i'm pushing it into sand. I've put various cleaners down the drain, which have helped some, even root killer. I put root killer down and the water that backed up was really brown for about a week, but now it seems to drain better. What could this sandy buildup in the bottom of the floor drain be, and is there anyway to clean it out? There is always standing water in this drain.

Logan

It may very well be SAND. You can take a wet/dry vac and suck the water out of the trap and then the sand/obstruction. Good luck.