Why use a peristaltic pump? ...

Why use a peristaltic pump?  If you're concerned about brackish water only, use a centrifugal pump with a fiberglass head, since pressure or viscosity aren't big factors.  A positive displacement pump uses much more energy than a centrifugal pump.  if you can gravity feed out of a tank or have any head on the pump inlet, you can use a centrifugal.  I would imagine using PV, you need to save as much energy as possible.