If the drain is still slow, you need a mechanical assist. Make a paste:
Sodium bicarbonate is an alkali (base) with a pH of roughly 9. Many drain odors are caused by bacteria that thrive in acidic environments or by the release of sulfur compounds. By raising the pH level within the drain, baking soda neutralizes acidic odors and creates a less hospitable environment for certain odor-causing bacteria. baking soda for cleaning drains