Another option is to just not use any filter at all
.
We used to think a filter would be beneficial and tried several methods. Under sink, external, cheap throw away, permanent residential type, several stages. Finally determined they were all more troublesome than they were worth.
They are expensive, can decrease water flow rate, and can actually make you sick if not maintained correctly. And in general they are just a PITA and one more thing to have to do.
So now, we are much happier not dealing with any water filters. We, as most of our RV group, use our fresh water tank mainly for bathing, washing dishes, and toilet. Use bottled water for drinking and coffee.
But this water usage option is just what works best for us, developed over decades of RVing across the country. Everybody has to determine what methods work best for them.
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Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD Duramax
Reese Fifth Airborne Sidewinder