First of all, it depends on where there is water leakage, generally in floor drains, pipe roots, corners, doorways and so on. You can judge the traces of water seepage from downstairs, just dig some tiles for waterproof repair, and the maintenance time is also very short;

If none of the above is true, it may be that the concealed pipe is leaking, so you can do pressure measurement to determine that it is a pipe problem and then chisel bricks;

If it is an old house with serious water leakage and prefabricated panels, the water is pervasive, and it is recommended to dig it out and waterproof it again;

Waterproofing by grouting on the back surface is really a temporary solution, not a permanent cure.

Regarding the equipment for detecting water leakage points, there is a device for detecting water leakage points of water pipes, also called "stethoscope".

It is suggested to find a professional waterproof company to solve the problem, sign a maintenance contract, and explain all the water-using equipment in the kitchen to the master during maintenance to avoid misjudgment.