I have a leak on the hot pipe in the wall in the kitchen. I have a system boiler with cylinder in bedroom. From what I can see there are 2 valve's by the cylinder. One valve which is on the pipe what feeds the cylinder from the header tank and another which is a gate valve on the bottom pipe by the cylinder. I am trying to leave the cylinder full but isolate the pipe to the kitchen so I can work on it . This way it will prevent me from dropping the full cylinder and possibly getting a airlock. I have shut the gate valve and then opened the downstairs tap but it is not isolating it. Am I missing something here ?[/b]