A double-walled contained shear valve comprises of an inner housing forming a fuel flow path, and a containment housing surrounding the inner housing, either partially or wholly, to provide a secondary containment. An interstitial space is formed between the inner housing and the containment housing as a result, and may be placed under a vacuum or pressure level to monitor for leaks. A vacuum actuator coupled to the interstitial space automatically opens and closes the fuel flow path of the shear valve in response to the vacuum level in the interstitial space to prevent leaks to the environment. The shear valve may contain a flange for connection to internal fuel dispenser piping that either does or does not includes interstitial space orifices to couple the shear valve interstitial space to the fuel dispenser piping interstitial space to monitor the vacuum or pressure level in these interstitial spaces as one contiguous space.