The answer to 'water line replacement won't flush' is that a common cause is debris or sediment buildup in the new water line after a replacement. Symptoms include low water pressure, slow draining, or the inability to fully flush the toilet or other fixtures. The solution is to flush the new water line thoroughly to clear out any debris.
If you've recently had your water line replaced, it's important to flush the new line before using it. This helps remove any dirt, rocks, or other particles that may have gotten into the line during the installation process. You can do this by running the water at full force for 15-30 minutes, flushing all the fixtures in your home. If the issue persists, you may need to call a professional plumber to further inspect and clear the line.