Many of our units come with 3 control knobs located on the control panel to operate the ‘water’ functions in the unit. The top control is a divertor valve, turning this will divert the water to the various functions in the shower such as the hydro massage jets, the Monsoon Shower head and the personal hand shower and on the whirlpool bath units, there is a 5th setting which fills the bathtub. (Please note, the unit divertor only operates one function at a time.) The middle control knob operates the pressure of the water, and the lower control knob is the thermostatically controlled valve which has a safety switch that stops it at 38 degrees. If the knob is depressed, the unit can be set higher than 38 degrees if required.