The Nelson 1000 Series 50mm pressure relief valve releases water when upstream pressure rises above the pilot setting. Its hydraulic sleeve and pressure-control pilot work together to relieve pressure and close again as pressure falls.
The pilot senses pressure on the upstream side of the valve. As that pressure exceeds its setting, the pilot allows the sleeve valve to open and discharge water. As pressure falls, the pilot controls the valve towards the closed position.
Used on a relief branch, the valve releases excess water rather than reducing pressure in the main supply line. Nelson also uses this upstream-pressure control principle for pressure-sustaining applications, where flow is controlled to maintain pressure before the valve.
The modular 1000 Series design uses a flexible internal sleeve as the closing element. The official documents include operating principles, pressure-loss curves, parts information and control-plumbing diagrams.
Nelson 1000 Series Catalogue 2026
Nelson 1000 Series Specifications, Performance & Dimensions
Nelson 1000 Series Parts & Service
Nelson 1000 Series Plumbing Diagrams
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