I have a 3/4 inch black mainline that is about 10 years old. At the end of every season I backwash this mainline and laterals with hot water ( I have access to a hose and hot water) and I do the same before using it in the spring. I use the long milk filters to filter the sap before it enters my holding tank. This year I am having problems with the filters catching all kinds of crap. As the season went on sometimes I would have to change this filter 3 times a day. I know late in the season and with the warm weather the sap gets kinds slimy but I am not having any out of ordinary problems with my other lines. ( 5/16 and 3/16 lines) My question is how should I clean this line? I'm thinking of filling the whole line up and letting it soak for a day or so but I don't know what to fill it with nor do I know what percentage of a solution I should use. Suggestions?