How to seal leaks from shower tile floors?

[thealfa]

The shower rarely got used as there's 3 bathrooms in the house. Upon cleaning the upstairs shower with soap and cleaning agents there was no visible holes or cracks on the flooring and no leaks. But upon first usage of the shower we saw water leaks on to the ceiling downstairs. The cracks or holes must be small for the leak to only show upon first use of the shower?

I've attached some pictures. I've zoomed in to one of the pictures and I think there's a small crack on the caulking of the shower tiles. Would a sealant like this work:

https://www.homedepot.com/p/GREAT-S...nsulating-Spray-Foam-Sealant-363103/202893739

But how do I find where the actual hole or crack of the shower tiles? I think they sell a product for cars that will illuminate if it detects a leak on pipes and hoses so I'm curious if such a thing exists for home repairs?

 

[havasu]

I'd be looking closely at the drain in the shower. Remove the cap and inspect shrinkage of the seal around the drain pipe.

 

[Steve123]

Grout is not waterproof.
That is why a shower is supposed to be waterproofed UNDER the tile.

https://www.finehomebuilding.com/project-guides/tiling/waterproofing-tile-showers

 

[Snoonyb]

Ah yes, back in the days of, and the fragrant odor of, hot-moped shower pans.

 

[thealfa]

I'd be looking closely at the drain in the shower. Remove the cap and inspect shrinkage of the seal around the drain pipe.

I'll try that in a bit. Is it easy to install a new seal around the drain pipe? I've never done this before.

 

[havasu]

I'll try that in a bit. Is it easy to install a new seal around the drain pipe? I've never done this before.

Won't know until we see the type of flange you have.

 

[Snoonyb]

Take photo of the drain, which may lead to advise regarding it's removal.

Some are easily removed with tools like these;
https://www.amazon.com/Remover-Wrench-Removal-Dumbell-Aluminum/dp/B08T8H37KS/ref=asc_df_B08T8H37KS?mcid=7d145d08e31430b0bf1e049bb83d5e15&hvocijid=10163691691136370310-B08T8H37KS-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw=g&hvrand=10163691691136370310&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9019557&hvtargid=pla-2281435180218&psc=1

https://www.amazon.com/Armour-Line-...s=hi&sprefix=drain+t+wrench,tools,119&sr=1-20

Which are retailed at several local venders.