Complete amateur so excuse the potential stupidness of this question! The valve on this radiator broke off when trying to open it. The radiator is empty and the both valves are closed. I believe this valve is on the return side, so would I be wrong in thinking that I could simply remove the broken valve and put on a new one without there being an escape of water? Or would the pressure in the system mean that regardless of it being the return side, water would still come ****ing out the moment I take the valve off? Thanks in advance.