Our shower recently had a hairline crack develop in the shower. The pan is made of river rock and it looks like the previous owner already added something to fix a previous crack. What should I use to fill/fix the current crack?

Any idea how the pan is built? How the pan is sealed?

I'm curious is this is a grout bed cracking over a vinyl liner or a painted on product on a concrete or mortar pan which could be indicative of a more through going crack?

I was thinking the same thing...the pan is leaking or uneven and the crack fighting is just beginning.

Yup the crack isn't the leak, it's a sign of the leak. 99% odds that the shower wasn't waterproofed properly and that they used a liner only, and I'd say 75% chance they didn't do that right either because I've never seen one that was.

If you're lucky you're looking at a R&R of the floor, if you're not you're the winner of a new shower. Either way, if the contractor tells you tile, grout, cementboard (even the new kind) or greenboard are waterproof you should mark them off your list because that's what got you into this mess to begin with. If they mention Schluter, Redguard, Kerdi, or some other ACTUAL waterproofing material because there's a couple others I forgot, that's the one you should pick.

I'd caulk it with clear caulking and use it until a problem showed up if you're on a slab. The only shower I've seen done right is ONE of mine but that's because I watched it being done and made requests as they went.

I agree with all comments above except that they are all guessing. There is only one way to know how that pan is constructed, unfortunately.

I'll throw out an alternative opinion. It's entirely possible the waterproofing was done correctly and this could simply be a crack in the grout due to foundation shifting/settling. (the other responses are more likely)

I didn't build, so I don't know how it was constructed. I am guessing there is no way to determine that without ripping up the rocks.
I haven't seen any cracked sheet rock or anything like that to point major shifts in the foundation, but there are some cracks in on the patio to suggest there is some movement of the slab.
I guess my plan would be to put some clear caulk on the crack and then monitor it. I will the reassess if more cracks start to develop?

You can also buy a caulk that matches your grout.

Could you pull the permit and inspection from when it was constructed? We just finished a reno with a new shower and the pan had to be inspected holding water for 24 hours before they could lay tile down on it. I'm pretty sure the construction is documented in the permit/inspection.

You need to test they shower pan by plugging the drain and filling it with water for a minimum of 24 hours. Any plumber can do this or you can DIY if you feel comfortable.


https://www.amazon.com/Cherne-270024-Test-Ball-2-Inch-Plug/dp/B000VYNU7A/ref=as_li_ss_tl?dchild=1&keywords=inflatable+test+plug+2+inch&qid=1588902107&sr=8-8&linkCode=sl1&tag=diytileguycom-20&linkId=9b5052727b511f38908159badb5a51a6&language=en_US






https://www.amazon.com/Cherne-270024-Test-Ball-2-Inch-Plug/dp/B000VYNU7A/ref=as_li_ss_tl?dchild=1&keywords=inflatable+test+plug+2+inch&qid=1588902107&sr=8-8&linkCode=sl1&tag=diytileguycom-20&linkId=9b5052727b511f38908159badb5a51a6&language=en_US


If the pan is not compromised then for cosmetic fixing of the cracked grout use a product like this


https://www.lowes.com/pd/MAPEI-Keracaulk-S-10-5-oz-Warm-Gray-Sanded-Paintable-Latex-Caulk/3033532