Mystery shower floor drain

[Stevevan]

Hi all,
I am a handyman at a fraternity building built in 1954. I have two identical showers, side by side, one will drain the other is clogged and has been for at least a year. They are like a drum trap in physical appearance but they aren't because they can never be accessed. They are built into a pre-stressed concrete plank that allows no access. On the valve/wall side of the drain there is an outlet at the bottom of the drain, based on drawings from Terry's website I believe this must look a bit like a teapot. The outlet must have a pipe that rises again from the bottom elevation because the drain seems to function as its own trap. I say that because the drain next to it has about 4 inches of water always sitting in it. I recently had a highly recommended drain specialist out and he couldn't get the drain opened up. Anyone have any thoughts, ideas?

 

[WorthFlorida]

A fraternity house? A prank could have been pulled many years ago. Google, removing concrete from pipes or concrete dissolver. Some are for surfaces and others for pipes. If you know the type of pipe you can try a jug of concrete dissolver.
What did the drain specialist do to try to unclog it. The picture seems to show dirt. Was a shop vac tried? The one with water suck it dry with a shop vac and then you'll be able to tell what type of trap it is and the direction of the drain.

Google "clog hog". It's a jetter that is used with a pressure washer. I used it to unclog a mop sink drain that was blocked for years from grease, sand and soaps that solidified into a solid at a wye under a slab. It took mechanical and jetting to clear the block. On the third time using the clog hog finally broke through the clog. Why is blocked up was the man a made grease trap before the septic field was never cleaned for over thirty years and the wastewater would drain very slowly or not at all.

 

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[Stevevan]

Thanks I think that might work, good thought, thanks!