Floor drain help

This floor drain is in the laundry room. I removed the cover to find this. Doesn’t seem that this would allow any water to drain. There appears to be a wing-nut holding this in place. Is this some type of back flow preventer or filter? Any help would be appreciated.

Looks like a plain mechanical plug. You twist the wing nut and it expands the rubber to seal off the opening.

So you loosen the wig nut and it allows it to drain?

Only if you take the plug out and put the strainer back on. For some reason they have stopped the use of this floor drain.

Thanks John,
Bad idea to plug it since it is in the second floor laundry room.

Did this bathrrom ever get remodeled? This could have been an opening for a closet flange for a toilet.

Hope the info helped.

It is not a bathroom, it is a laundry room. Unknown if it was remodeled. Previous owner is deceased and the seller did not know. It did help. Thanks

At some point the water evaporated out of the trap and the homeowner put the plug in it to eliminate the odor (instead of just pouring water into the trap). That’s why the flloor drains in my house don’t tie into the sewer system, but drain independently to the outside instead.