How Flow regulators work
Flow regulators are used to maintain a defined flow rate regardless of pressure variations of the supply line. Precise flow control improves system performance and, in the case of plumbing systems, it provides comfort of use at low pressure as well as water and energy savings at high pressure. When there is no flow or pressure, the o-ring is relaxed. When there is normal pressure, the o-ring subjected to the line pressure is compressed into the seating area. As the pressure increases, the o-ring is compressed further into the seating area. As the pressure decreases, the o-ring relaxes.
Since the flow rate for a given orifice changes to the square root of delta P, the o-ring deformation is equal to this, giving a constant flow over a wide range of pressure variations.