How often do you clean your evaporator pan?

[eustis22]

I clean with hot water and vinegar every four boils (alternating flow).

[mainebackswoodssyrup]

We clean our 2x2 syrup pan every +/- 500 gallons through it at the maximum, never more than 2 boils between cleanings. We had a 2nd syrup pan made last year which has been great. If we have a boil around 300 gallons and expect more sap soon, we'll just do a pan swap after the boil and be ready to go for the next one. We let the dirty pan soak and clean it during the next boil so we always have one ready to go.
Occasionally we will give the flue pan a hot water rinse mid-season but usually don't bother as we need to make a dark syrup anyway. Even so, I believe what we have in the pot now will be a light dark. Last year we put 3300 gallons through the machine and never dropped below LT 45.