Abstract purity and defilement are also expressed in water-terms of "qing" clarity; standing water that is lucid to the bottom and "zi" dregs; sediments; defilements.
One custom that may be disturbing to the visitor's notions of hygiene is that of pouring the dregs of each cup back into the "kumis" storage container.
In medieval cosmology, the sump was the center of the cosmos, where the dregs and filth descended, with the celestial sphere far exalted above the world of fallen man.