I removed a broken 4x4 drain tile at the circular drain. Under it, I found something like sand filling the approximately 15" hole through the slab for the drain. It was very damp and even had tree or shrub roots in it. It seems that the drain is actually under the slab and comes up through this hole. Should I remove the other 3 tiles around the drain and fill it with concrete? I'm sure the tile ultimately broke because about 1/3 of it was resting on this sand.

Or was it just a very poor concrete mix that eventually crumbled to resemble sand? I live in Tampa so there really isn't dirt under the slab, just sand.

Was this a floor drain or part of your sewer drain?

It is the drain in the floor of a tiled shower.

Greetings from Sarasota,
I worked in Tampa back in the 60's. I plumbed a lot of your condos and single family homes.

I removed a broken 4x4 drain tile at the circular drain. Under it, I found something like sand filling the approximately 15" hole through the slab for the drain. It seems that the drain is actually under the slab and comes up through this hole.
This "drain under the slab", was it actually a trap?
Sounds like what you have is a tub dap out converted to a shower. The hole should have been filled with cement before the shower floor went down. I would fill the hole and replace the tiles. Good luck, Tom

Tom, the shower stall appears to be designed in as it is recessed 3" from the bathroom floor and there is a separate tub. If I fill it should I use concrete or sand?

Tom, the shower stall appears to be designed in as it is recessed 3" from the bathroom floor and there is a separate tub. If I fill it should I use concrete or sand?

Cement. Good luck, Tom