The current flush toilet always uses a siphon pipe to suck/discharge a sewage and to isolate the smell gas. During the discharging, water is firstly filled into the water tank to replenish as a level to the top of the siphon pipe. When discharging a large amount of water to expel the air in a water discharging pipe of the siphon pipe in order to form vacuum such that a pressure difference is produced between both ends. Finally, sewage together with water is discharged into a sewage-discharging pipe by the atmosphere pressure. In regard to the sewage-discharging pipe, the sewage in the flush toilet bowl is sucked into the sewage-discharging pipe and discharged by the sewage-discharging pipe.
The higher the top of the siphon pipe in the water tank, the larger the diameters of sewage discharging pipe, then the more water needed in generating the vacuum. Since the water needed is to generate the vacuum only, water is a “pro-waste” for this single purpose on discharging sewage. It is a disadvantage in the environmental protection and in the full utilization of water resource. Especially, it should be fonder of water in water-deficient areas. Another function of the siphon pipe is to retain water below a level of the top of the siphon pipe to isolate the smell gases flowing into a room so as to keep the flesh and clean of the air in said room.
The current siphon pipe type flush toilet must be provided with a water tank to store a large amount of water to be flush out in a short period so as to generate vacuum in the siphon pipe. If there is no water tank, it still is possible to form vacuum in the discharging end of the siphon pipe for the high-pressure water source, but does not work for a low-pressure water source. That is, the amount of flushing water is not enough to expel all air in the discharging pipe. In the other words, the replenishing water is not as fast as the discharging water. For the high-pressure water source, although it is possible to provide a large amount of water to form the vacuum in the siphon pipe, the discharged water should be deemed as waste.