Control valves will be fitted to each end of the radiators in your home. Designed to open up and close down the radiator and the other valve which is a lock shield valve is fitted at the other end of the radiator body and will not adjust. It has a plastic dome shaped cap. Enfield Plumbers can fit radiator valves.The control valve, may consist of a simple plastic topped control valve for on and off operation or a TRV, better known as a thermostatic radiator valves. For years it has been the heating system installer who has decided whether to use a manual valve or thermostatic radiator valve, but nowadays the Building regulations dictate that TRV’s must be fitted. The only radiators that can be fitted with a manual valve is those connected to radiators in rooms where a room thermostat has also been sited. This valve automatically closes off the water to the radiator when the desired temperature in the room is found, this gives a good saving on fuel and also makes sure that heat is not supplied in a wasteful manner. The lock shield valve, which is at the other end of the radiator, has a very specific job and that is to control the amount of water that flows through the radiator. This valve however has been pre-adjusted using a spanner at the time of installation during balancing of the system.Balancing:To make sure that the first radiator in the line will not take all the hot water from the boiler, as it is the shortest route, the lockshield valve is partially shut. Having this valve open by only half a turn, the water is forced to continue along the heating circuit to the next one. So the radiator lockshield valves are also adjusted as required to force the floor water throughout the whole system. EN2Plumbers can balance a heating system.