The time it takes for bleach to kill weeds can vary, but typically it may take between 3-7 days. Bleach primarily works by drying out the foliage of the weeds, which can lead to their eventual death. While bleach may show visible effects on the weeds within a few days, it may not completely eliminate the root system of the weeds, allowing for potential regrowth. For more effective and long-lasting weed control, it is recommended to use herbicides that are specifically formulated for weed eradication.