A valve symbol legend is a drafting reference, not a substitute for the project specification or valve schedule. It helps designers, engineers, and CAD technicians apply consistent graphical conventions across process, plumbing, HVAC, and mechanical piping documents.
Use the downloadable DWG alongside the project’s drawing standards and approved P&ID or MEP templates. Before issuing a drawing, confirm that each symbol communicates the intended valve function, operating method, and connection to any related instrument or control system.
This Valve Symbols Legend CAD sheet is a useful reference for P&ID, process, and MEP drawings. It includes a wide range of standard valve symbols and related items so your drawings stay consistent and easy to read for engineers, installers, and commissioning teams.
The legend covers many common valve types used in mechanical and process piping, such as:
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Gate valves (hand-operated, motor-operated, closed gate)
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Globe valves (hand-operated, angle globe)
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Ball valves (including normally closed ball)
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Check valves and variations
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Butterfly valves
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Control valves and powered/actuated valves
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Solenoid valves and pilot/float-operated valves
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Relief / release valves, back pressure regulator
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Plug/cock valves, diaphragm valves, needle valves
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Specialty items like pinch valve, bleeder valve, knife/slide valve, metering valve, orifice, rotameter, water flow meter, and more
Use this CAD legend for:
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P&ID and process documentation sets
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MEP plumbing and HVAC piping drawings
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Training junior drafters on correct valve symbols
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Standard templates for consultants and contractors
How to use a valve symbol legend in CAD
Start by identifying the piping service and drawing type, then select the symbol that matches the valve function shown in the design. The graphic should be read together with the line, flow direction, equipment tags, instrument bubbles, and any notes that define operation.
Check symbol meaning and operating method
Valve symbols can distinguish manual operation from motor, solenoid, pilot, float, or other actuation. They may also indicate a normal operating position or a special function. Do not infer the complete valve specification from the symbol alone; verify the valve tag, schedule, datasheet, and project notes.
Coordinate the legend with related drawings
For P&IDs, compare valve symbols with instrument and control documentation so isolation, regulation, relief, and measurement functions remain clear. For MEP drawings, coordinate the legend with plumbing, HVAC, equipment, and riser documentation. A consistent symbol set reduces ambiguity during detailing, installation, inspection, and commissioning.
Practical CAD review checks
- Confirm that the symbol is legible at the intended drawing scale.
- Use consistent block orientation, insertion points, layers, and annotation practices within the project template.
- Check that valve tags and nearby notes do not obscure the line or symbol.
- Compare repeated symbols across plans, schematics, details, and schedules.
- Follow the project legend when it differs from a general reference convention.
What this DWG reference does not define
The CAD legend communicates graphical intent. It does not by itself establish valve material, pressure rating, end connection, sizing, flow capacity, control logic, or suitability for a particular service. Those decisions require the applicable design documents and engineering review.
Valve symbols legend CAD FAQ
What is a valve symbol legend used for?
It provides a consistent graphical reference for representing valves and related piping or instrumentation items on P&ID, process, plumbing, and HVAC drawings.
Can this DWG determine which valve should be specified?
No. The DWG helps communicate the selected function and operating arrangement, but valve selection must be confirmed against the design requirements, project specifications, schedules, and engineering documentation.
Why should a project legend be checked before using a standard symbol?
Projects may define their own symbol conventions, tagging rules, layers, or annotation methods. The approved project legend takes precedence when it differs from a general CAD reference.
How should valve symbols be reviewed on a P&ID?
Review each symbol with the associated line, flow direction, equipment, instrument tags, control connections, notes, and valve schedule. Confirm that the drawing clearly communicates both function and operating method.
Can the same valve symbol be used on MEP and process drawings?
A symbol may appear in more than one drawing discipline, but its interpretation must follow the applicable project convention and the information required by that drawing set.