How often should I clean lines that are used to transfer sap? I have two lines that I am dumping sap into that flows downhill and empties into a container. Sap is in it for just a short time before it empties and stays empty. Do I have to worry about bacteria growth in that empty line? Also what about those of you who are pumping sap from collection tanks into other tanks using a non permanent line. How often do you clean those lines and pump? Do I need to worry about bacteria growth there?