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A pair of check valves with a relief.
Also known as: Reduced pressure zone valve symbol, Anti-contamination valve symbol
The plumbing drawing symbol for a device preventing contaminated water returning into the supply.
Marks a device preventing contaminated water returning into the supply on a plumbing drawing.
Contexts: Technical drawing
Draws two valves and a relief rather than one device, so the symbol records the redundancy that makes the protection acceptable to a water authority.
Contexts: Technical drawing
Two check valve symbols in series on the pipe line with a short relief branch drawn between them.