The answer to 'how to maintain drain' is to regularly clean and maintain your drains to prevent clogs and slow drainage. This includes using a drain snake or plunger to clear any blockages, flushing the drain with hot water, and using a drain cleaner or baking soda and vinegar solution to remove built-up gunk and debris.
It's also important to be proactive and prevent clogs in the first place by being mindful of what goes down your drains. Avoid pouring grease, oil, or coffee grounds down the sink, and use a drain cover or strainer to catch hair, food particles, and other debris. Regular maintenance can help extend the life of your drains and avoid costly plumbing repairs down the line.