The invention discloses a variable-water-volume pure-water waterway 
system. The variable-water-volume pure-water waterway 
system comprises a first water 
inlet valve, a front 
filter element, a water pump, a reverse-
osmosis filter element, a controller, a first concentrated-
water channel and a first pure-
water channel. The first water 
inlet valve, the front 
filter element, the water pump and the reverse-
osmosis filter element are communicated sequentially. The first concentrated-
water channel is communicated with a concentrated-water end of the reverse-
osmosis filter element, and the first pure-water channel is communicated with a pure-water end of the reverse-osmosis filter element. A fourth water 
inlet valve and a 
mass-flow concentrated-water valve are arranged on the first concentrated-water channel sequentially. A fifth water inlet valve and a high-
pressure switch are arranged on the first pure-water channel sequentially. The variable-water-volume pure-water waterway 
system is characterized in that the variable-water-volume pure-water waterway system further comprises a 
backflow channel, a second concentrated-water channel and a second pure-water channel; the 
backflow channel is communicated with a water inlet end and a water outlet end of the water pump, the second concentrated-water channel is communicated with the concentrated-water end of the reverse-osmosis filter element, and the second pure-water channel is communicated with the pure-water end of the reverse-osmosis filter element; a second water inlet valve, facing the water inlet end of the water pump from the water outlet end of the water pump, is arranged on the 
backflow channel; a third water inlet valve and a small-flow concentrated-water valve are arranged on the second concentrated-water channel sequentially; a quick heating module is arranged on the second pure-water channel; all the electric elements are connected with the controller electrically.