Need a bit of help. The brine piston in my Fleck 2510 control head is stuck and won't move in or out. Is there any way to free it or should I replace the brine assembly? The piston is gray plastic and the assembly that it fits in is brass. If I need to replace it, can you tell me how to remove the assembly? The brass assembly appears to have shoulders for a wrench. Do I put a wrench on it and unscrew it to get it off? I don't want to force it and break something. Thanks for your help.