Reliable and durable. Simple internal structure, fine workmanship. Apply to: Hydraulic instability, water flow too fast, water purifiers, solar energy, gas heater and faucet. Valve working principle can be simply understood as the entrance pressure and outlet pressure = spring force, through the control valve closure flow inside the opening of the size to control the pressure at the outlet, the water through the opening, closure and fluid resistance is small, the pressure loss is small, the outlet pressure is greater, and vice versa outlet pressure is small.