Rheem eco200dveln3-1 tankless propane water heater question

So im installing a Rheem eco200dveln3-1 tankless water heater in a commercial building.199,000 btu. the engineer left it up to me(after i showed him how much sediment and calcium were inline) to figure out what kind of sediment filter to put on the inlet water line. Any thoughts?Thanks in advance!

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