The answer to 'shower overflowing' is that there are several common causes, including a clogged drain, a problem with the shower diverter valve, or a blockage in the plumbing system. Symptoms may include water spilling out of the shower enclosure, slow draining, or the shower backing up when the tub is drained.
For minor clogs or issues, you may be able to resolve the problem with DIY methods like using a plunger or a drain snake. However, if the issue persists or you suspect a more serious problem with the plumbing, it's best to call a professional plumber to diagnose and fix the problem. Attempting complex plumbing repairs without the proper skills and equipment can lead to further damage or safety issues.