Do not throw old coffee down the sink
Has your dentist ever told you to avoid drinking tea or coffee to keep your teeth from getting stained? Well, the same principle applies to porcelain, which is why you should avoid pouring it down the toilet or a sink made out of that material. In fact, you should avoid throwing it down the drain entirely.
Believe it or not, ground coffee beans liberate quite a bit of fat, which can cause fatty build-ups that clog your pipes and require professional help to remove. Instead, try pouring it on the soil in your garden since it works as an effective fertilizer. You can also do that with used coffee grounds.