The coffee grounds in the moka pot can be boiled up to 1 time, not repeatedly. Because the water-soluble substances have been dissolved, you can discard the coffee grounds. The part of the substance that is not soluble in water is not called coffee, and it is harmful to the human body if consumed for a long time. If you think that the coffee residue discarded, can be dried and stowed in the sun to do surfactant in the refrigerator to adsorb odor use.