DC Submersible Pump

The Robinson DC powered submersible well pump can be found here: http://www.solarpumps.com/products.html You would want the smaller of the two about half way down the page " Dual piston BL40D (535240)" It runs off of DC power from 12 - 40 volts and will fit down the 4" well you have. The larger quad piston pump is too large to fit in the 4" well. I would put that in the well you have and pump the water over into the old rain catchment system and see how far that gets you. If you end up needing a new well the Robinson pump can be used in it. There are a few lower cost DC powered well pumps out there but they seem to fail within a matter of months whereas the Robinson last much longer and is rebuildable. Grundfos makes the best DC powered submersible well pumps but they cost twice as much as the Robinsons.

The permeate pumps I use on RO units are like this one: http://www.ebay.com/itm/Permeate-Pump-for-Reverse-Osmosis-ro-r-o-filter-/290 380092394 They greatly reduce the wasted water, and increase the life of the pre-filters. I think RO unit you had took standard (2.5" x 10" nominal filter elements) prefilters so you can get them off of ebay and don't need the special kit from Home Depot. Measure them to make sure. The RO membrane is most likely a "1812" series with a measurement of 1.75" x 11.75". You can get up to 100 gallon per day membranes that will fit in the same size housing, but you do need to change the flow restrictor if you install a higher output membrane.