The answer to 'water line won't flush' is that there are several common causes, including a clogged toilet, a problem with the plumbing vent, or a blockage in the main sewer line. Symptoms may include the toilet not flushing properly, slow draining, or water backing up. Solutions can range from simple DIY fixes to more complex professional plumbing work.
If the issue is a clogged toilet, you can try using a plunger or a toilet auger to clear the blockage. If that doesn't work, you may need to disassemble the toilet to access and clear the clog. For problems with the plumbing vent or main sewer line, it's best to call a professional plumber, as these issues can be more complex and may require specialized equipment or expertise to diagnose and repair.