Shower – the cause of a shower diverter valve becoming stuck

Your diverter needs to be replaced - in your case, this is part of the spout. The diverter is responsible for allowing water to flow out of the tap, or when engaged, it closes the spout and forces the water up through the shower head.

You can try to disassemble it and find a replacement part, but often it is easier to just replace the entire spout.

Usually the spout is held onto a piece of copper pipe with a set screw in the bottom of the spout. Loosen the screw (usually with an allen key) and pull away from the pipe. Replacement is the opposite - twist onto the pipe, align it properly and tighten the set screw.

You might not find an exact replacement but any spout with a diverter in it should work.

This should be a pretty cheap and easy replacement. Good luck!

Diverting the leak up to the shower head using the diverter valve should not be a problem, but your assumption that fixing it will be "pretty easy" may not prove to be true. You are correct in that hot and cold supply to the tub/shower valve needs to be shut off. Sometimes apartment shower valves have built in shut-off valves called integral stops.

Sometimes apartments are equipped with individual remote shut-offs. Sometimes the whole building will need to be shut down. Removing the valves may require special tools like deep valve sockets.

The repair may be simple washer replacement or may require more complicated cartridge replacement.

I do recommend that you try it but make sure your landlord is cool with it in case something breaks, and have back up shower facilities available in case it ends up being out of service for a while.