With toilets that run water, wastewater is full of a lot more organic matter than in toilets that are dry, in which wastewater is nearly inexistent. This material will compost on the vertical filter and accumulate with time. Every 10 to 20 years, a few centimeters of settled organic matter should be collected, which will make a very good amendment for the soil. It is recommended to undertake a supplementary compost cycle for this material because it will be overrun with reed rhizomes. The rise in temperature provoked by the degradation of the manure will destroy the germs.