Abstract: A nozzle (10) has a diaphragm valve (50) mounted at or near the downstream end of the spout (20). The diaphragm has an opening (56) responsive to fluid pressure in the spout, allowing fluid to pass with sufficiently high upstream pressure and preventing fluid, from passing with lower upstream pressure. The opening can have any suitable shape and size, but is preferably multi-branched, with a central point from which side openings radiate. The diaphragm is preferably place very close to the down-stream end of the spout to reduce dead space, and may advantageously be included in an installation frame (80B).