Septic tank
While a properly maintained and located septic tank does not pose any more environmental problems than centralized municipal sewage treatment, certain problems can arise with septic tanks in unsuitable locations. Since septic systems require large drainfields, they are not suitable for densely built areas.
Weeping tile
Weeping tile is used for the opposite reason in the septic drain fields for septic tanks. Clarified sewage from the septic tank is fed into weeping tiles buried shallowly in the drain field. The weeping tile spreads the liquid throughout the drain field.