I was just trying to get some Pro's thoughts on, why there would be a shut off valve on the hot line going out of my hot water tank, and no valve on the cold coming in? Is there a reason for this? Is it OK to add a valve on the cold,so I can isolate the tank, by shuting both valves , and would the 3/4 " sweat joints hold under pressure if I want to disconnect and change tanks? I see the same set up a lot at other sites. Thanks for any clues you guys have! Even the shut of on the cold would serve me better! It seems.