Abstract: A surge reliever relief valve is provided in which a flexible membrane is maintained in a peripherally sealed relationship across a rigid grid. The grid bounds the laterally adjacent intake and output regions of the valve. Intake pressure extends the membrane allowing flow between intake and output. Extension of the membrane is limited by a retainer. Extension may be elastic or inelastic.

Abstract: In a valve wherein a flexible tube is stretched around a circular barrier between inlet and outlet slots and is conditioned to enable flow in an annular path around the barrier when upstream pressure overcomes pressure in a control jacket around the tube, the improvement comprising a second flow path directly through the barrier, which is normally closed off by a poppet valve engagable with a seat around the passage. A spring augmented by a control pressure biases the valve toward closed position and is preferably set so that, only after capacity of the flexible tube is reached or approached, does the poppet valve open to answer the need for high pressure demand downstream or for relief of a high pressure surge upstream.