PURPOSE: To provide a sanitary sewer feed device strong against earth pressure or water pressure at a low cost and to make it possible to drain efficiently without causing detention by making the existing digestion tank body as a reservoir, and reinforcing an internal wall surface thereof to form the reservoir of water impermeable membrane.

CONSTITUTION: Sanitary sewer is fed to a sewage plant, etc., from a reservoir 1 by using the existing digestion tank body. At that time, a synthetic resin layer is applied on the internal wall of the digestion tank body to reinforce, and the inside of the digestion tank body of the reservoir 1 is formed of water impermeable membrane. The existing digestion tank body is used for the reservoir 1 by reinforcing it with a reinforcing layer only, and the digestion tank is unnecessary for back filling and is feasible at a low cost. When sanitary sewer in the reservoir 1 is pumped up with vacuum system, a pump P is omitted and, at the same time, a vacuum equipment is provided, and a vacuum valve is mounted on the inside of the reservoir 1.