In order to gain occupancy, an inspector informed me that I need to install a vacuum relief valve on the cold water supply line for my hot water tank. I purchased a vacuum relief valve and the installation instructions that came with it states that it should be installed on a horizontal line above an elbow... (directly above the vertical line that feeds the tank) My hot water tank is under the stairs in my basement so there is no room above the elbow for that valve. Does it matter where I install the valve? Can it be somewhere else on the cold water line? Or will I have to move the cold water line so its lower? I guess Im actually asking for clarification about the function of this valve... Thanks!