Options other than completely draining all pipes in a raw water system include isolating and dewatering the intake only or providing an undesirable intake water environment when the system is out of use. Installation of a swivel joint on smaller diameter intakes permits the intake to be lifted out of the water (dewatered) when the pump is not in use. This design modification exposes the intake pipe to ambient aerial conditions and, subsequently, leaves residual water in the system stagnant. Other methods to produce undesirable water environments include the placement of a larger pipe over the intake and angled 90 deg downward to produce a still well effect or the lowering of a larger pipe sealed at the upper end to trap air over an intake facing upward, exposing the intake to the atmosphere. In any of these three cases, the intake pipes would have to be uncovered or returned to operating position before use.