The role of the check valve in the pump water supply system is to prevent the impact of high pressure water return on the pump impeller. The system is running for some reason, the pump suddenly stopped running, the pump pressure disappears, and the pump outlet connected to the high pressure water will reverse flow back to the pump. When the pump outlet is equipped with a check valve, it closes immediately to prevent high pressure water from flowing back to the pump.
The function of the check valve in the hot water system is to prevent hot water from flowing back into the pipe. If it is PVC pipe is likely to burn pipe, and may even hurt, especially in the solar water heater system.