I use 3/16 and mainline after it flattens out. I usually get some debris from tapping and a little gunk from last year. Like another said, I change mine daily with a spare filter. I wash up the gunky one with a bottle brush and its ready to go. In warmer weather there is a little more gunk but that is normal. And just because sap is cloudy doesn't mean it is bad. Most warm spells I boil cloudy sap and it always turns out fine. When in doubt, if the sap passes the smell and taste test you are good.
On the recirc line, I had one a few years ago but found I didn't need it as there was enough flow from the taps it didn't make a difference.
Camp Wokanda
Peoria Park District
2023 - 210 on 3/16 shurflo, sap storage shack w/ 1100 gallon tank - 123 gallons
2022 - 210 on 3/16 shurflo, homemade vac filter & water jacket canner - 104 gallons
2021 - 215 on 3/16 shurflo, added 2nd membrane to RO - 78 gallons
2020 - 210 on 3/16 shurflo, upgraded hp pump on RO - 66 gallons
2019 - 150 on 3/16 shurflo, Deer Run 125 dolly RO - 73 gallons
2018 - 120 on 3/16 shurflo, 2x6 raised flue w/hood, homemade arch w/ AUF & AOF - 34.5 gallons