You probably and hopefully have a large amount of sand grout stuck in the p trap if so your best bet would be to remove the p trap and give it a good thorough cleaning out in the yard with a hose.
How to dissolve grout in drain pipe.
It causes blockages by settling in p traps and pipe joints and hardening into a clump.
One option when dealing with a drain clogged with concrete is to pour muriatic acid down the affected drain.
We have septic and bathroom is small and no windows so don t want to use acid.
Tile grout can present real problems if allowed to accumulate in your drain lines.
A common problem is how to clear concrete from drain pipes.
Let it sit for two or three hours flush the drain with about 4 gallons of water then use a plunger to loosen the clog.
If the line is plastic you may be able to break up the grout and push it down to a larger line.
Since grout sets up under water you may have to get a licensed plumber with powerful sewer and drain cleaning technology to try and clear the line.
While the trap is off you ll be able to inspect the tailpiece and the drain line as it goes into the wall and clean those up too if necessary.
Hot water will not work to remove grout.
Any product that would dissolve dirt and clay lodged in a drain pipe would also attack the system itself at some juncture.
Not sure how much is really in there but it took hours for the pan to drain after first shower after project.
Tilers are meant to dispose of their grout in the bin but sometimes they can be lazy and let it fall down the floor waste or allow it to fall through the grated drain and this can cause major blockages to the pipe.
The other cause can also be tiler s grout which sits like concrete in the pipes.
The acid will attack the lime in the concrete and break it up.
I have been involved several times in the last 30 or so years where a tradesman has washed cement based grout down a stormwater or sewer drain expecting it to simply disappear never to be seen again.
Trouble is that it certainly was seen again.
Most older sewer lines are made from clay and even most newly built structures with pvc drain lines eventually discharge into a city waste system comprised of clay pipes.
As with many construction sites and new home building sites during the construction operations in order to maintain machinery and equipment in the good working order it is often washed down after use.
Unfortunately concrete and grout are what we use to make larger sewer lines.