I'm planning on adding a charcoal filter prior to the watermaker to remove chlorine. As long as I'm adding it, it seems reasonable to filter all the fresh water for the boat.
Does anyone have an idea how much a 10" carbon block filter (like this: https://airwaterice.com/filters/10-5-micron-carbon-block.html) would reduce the flow and pressure at the faucets in the boat? We have the Marco UP3 4gpm fresh water pump and it seems to do well without the filter. I just don't know how much reduction in flow I'll have with the carbon filter in line.
I checked the flow at the kitchen tap at 1.5gpm, but the pump was not running at full speed so it's hard to tell what it could pump with more head loss from the filter. In the forward head it was at 3.0gpm. With both the kitchen and fwd head faucet on the flow from the galley faucet total flow was 3.2gpm. Looking at the Flow vs. Pressure diagram from Marco, the pump is operating toward the high pressure side of the pump curve.