 In some cases, a so-called "bypass valve" acts as a relief valve by being used to return all or part of the fluid discharged by a pump or gas compressor back to either a storage reservoir or the inlet of the pump or gas compressor.This is done to protect the pump or gas compressor and any associated equipment from excessive pressure.The bypass valve and bypass path can be internal (an integral part of the pump or compressor) or external (installed as a component in the fluid path).