Hi Polaris after re-reading your entries, if the anode is in the supply line then it cannot protect the tank, you have to get the anode into the tank. I am also a little confused as to how the air is getting in through the anode corroding.If air is getting in then then water should come out. If air is getting into the tank then this is another likely source for your problem. Although as you mention the anode is deteriorating really fast then you do have some problematic water issues. Yes you will notice leaks more on the welds than the main body of the tank but not always. As I mentioned before it is probably more common on the welds in the upper portion of the tank. I believe that I have seen only once a leak on the bottom weld of the tank, and yet the welds are completed by the same welder same machine within 10 mins. Occasionally you can get them on the main body. Its very unlikely that your plumbing pipes will corrode and leak as they are not storing water just carrying it to and from. I am surprised that your brass drain valve leaks, you must have some bad water or problems with the quality of drain.