water pressure high after using hot water
Interestingly, working check valves (you noted in the other question that they were replaced) are essentially what cause this problem, your water heater is raising the temp of the water in the system (it's expanding) and it has nowhere to go, it can't flow back toward the street to equalize pressure thanks to the backflow preventing check valves, so it builds. 

This is exactly what hot water / thermal expansion tanks are meant to mitigate. You either don't have one or yours is malfunctioning. They are typically made of a tank pressurized with air and a bladder inside to let the water push against it as the pressure builds, since air compresses relatively easily compared to water.  If there is a leak on the air side of this tank, it will fill with water and not react at all to the changing pressure.