I have a solar hot water heating system that has a German tank. I need to replace the anode rod. I'm not sure of the manufacturer of the tank but model number is ESS-PU-300. I found an old price list from www.huch.com that includes some specifications. I'm trying to figure out what anode rod to order. The specifications make reference to "Magnesium protection anode of 1¼’’ The rods I'm finding available in the U.S. have a 3/4" pipe thread and it appears most have a 1 1/16" hex head for removal. Will these work or are the pipe threads metric on this hot water tank? I'm hoping to find this out before draining the system and pulling out the rod. Thanks for any help you can give me.