I think I have a common problem of hot water coming from a combi boiler and cold from a header tank. Hence when using a mixer switched to shower there is very little control of the hot water flow in order to have a reasonable temperature. Will a check valve in the cold water feed just before the mixer resolve this problem? If this will work does the cold water feed need to be at a minimum pressure in order to overcome the spring in the check valve and the pressure of the hot water attempting to close the valve? Thanks