Instead of directly connecting the main AC line to a pump chosen for specific fixed flow characteristics, the Decent machine uses over-specced pumps capable of hitting 19 bars of pressure with high flow rates. The machine monitors the AC line to detect the "zero crossing" of the electrical current. This allows the system to split the power into individual AC pulses, controlling exactly how many pulses are sent to either the hot water pump or the cold water pump.
The hot and cold water lines feed into two rectangular structures stacked on top of each other. Made of a high-performance polymer called Ultem, these components are drilled with a series of holes and are referred to as the auxiliary (aux) manifold and the mixed manifold. This is where the physical water mixing takes place, monitored by dedicated temperature sensors measuring the water both coming in and going out.
The machine monitors the water temperature in two phases: initially before the espresso shot begins, and then directly inside the group head once brewing is underway. If the sensor detects that the water is shifting even slightly too hot or too cold, the software instantly adapts. It changes the mix by commanding a few more cycles (or pulses) from either the hot pump or the cold pump to immediately correct the temperature.
The tubes running through this mixing section are designed with an incredibly narrow internal diameter of just 1.2 millimeters. By keeping the tubes so thin, there is very little volume of water resting inside them at any given time. This minimal water volume allows the machine to change the hot-and-cold mix almost instantaneously, responding rapidly to real-time sensor data without having to flush out a large reservoir of mismatched water.