Hi, I have an old shower, one of those with old lead pipes. The problem is the following: When you open the hot water tap, it takes time to leave, but then it comes out very hot. This is why I start to open the cold water tap, and then start regulating. The problem arises there, since by wanting to regulate, moving the tap by millimeters, the water changes drastically from being boiling to being warm / freezing. I recently changed the stems of the 3 faucets, hot cold and the middle one (the one that decides if it comes out of the shower flower or the faucet below), but the result remains the same. I would like to have a greater margin at the time of opening the cold, and that the temperature change is less drastic. Any idea what might be happening? From already thank you very much!