The freshwater line runs to the electric pump, then to a union. The city-water connection runs to this same union. There will then be a single water line running from that union to the filter housing, which then feeds the rest of the camper. In my SV, all fo this is in a single cabinet, with the exception of the water tank, which is in the adjacent dinette seat.
Find your water heater and/or water pump, and you should see the filter.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller