I gather that the trv should be fitted on the flow side of my new towel rail but on my old towel rail it for some reason was fitted to the return side. I will have to alter the pipework to fit it on the flow side so is it acceptable to leave the trv on the return side. Also the reason for me replaceing the towel rail was that it had sprung a leak through the bottom rung me the rail. When I drained it the water was very black and quite a lot of sludge came out. Could this be reason for the corrosion causing the leak? Its a ex council flat which runs from a communal system. Does it require flushing? Thanks