Thanks in advance everyone but after several hours of research I have gotten no where. My water softener is just one tank under the house. no other tanks or hoses coming out of the Fleck 5600 Filter Only Backwash Control Valve. There is a large maybe 1-1/4 plug in the top of the tank. I need too know where to add the salt. Been paying someone for 12 years and I am very mechanical inclined but this had stumped me as to where to add it I did pull that plug after I but the valve in service and tank was full of water. Stuck a stick down in and went close to the bottom. Any help would be great. I have no name of model number as the guy servicing it took all that off. Had a plumber look at it today and he had no idea either. But he was a well pump type of plumber. Tnakks