If the water is going to be reasonably clean ( not too many trees close by ), you could try a duel gradient cartridge using only one housing.
This cartridge has an external filtration size of 25 microns and merges to a final filtration of 1 micron at the inner core. Many people use these cartridges and it can be an economical method avoiding the need for a second housing & cartridge.
System consists of:
Jumbo 10 Inch Casing
Duel Gradient Cartridge - Remove Dirt & Sediment with Quality Water Purification
Splenvue SE12 UV Sterilizer - Kill Bacteria and Micro Organisms @110 litres per min