Plumbing & Piping Symbols Guide

84 symbols used on plumbing and piping drawings — from fixtures and valves to pipe connections and structural context. A reference for reading and reviewing mechanical plumbing plans on construction documents.

What Are Plumbing Symbols?

Plumbing symbols are standardized graphic representations used on construction drawings to depict piping layouts, fixture locations, and equipment within a building. They communicate the complete plumbing design — including water supply, drainage, gas lines, and vent systems — in a compact visual language that every trade on the project can interpret.

Plumbing plans show how pipelines connect within walls, under slabs, and through chases to supply water and gas, provide drainage, and prevent pipeline damage. Accurate symbols allow plumbers to locate equipment, verify pipe sizes, and coordinate with other trades before any work begins on site.

Common Uses of Plumbing Symbols

Indicating pipe sizes, materials, and routing on floor plans
Showing supply entry points and drain exit paths
Distinguishing hot water, cold water, gas, and waste lines
Locating fixtures, valves, and mechanical equipment
Coordinating plumbing routes with structural and MEP systems
Tracking installation timelines and scheduling inspections

Plumbing Fixture Symbols

Core plumbing symbols representing fixtures, tanks, heating equipment, and bathroom components found on plumbing plan drawings.

Boiler

Rectangular vessel outline

A fuel-burning apparatus or container used to heat water or generate steam for building heating systems.

Heat Exchanger

Circle with internal curved line

Transfers heat between two fluids without mixing them — commonly used in hydronic heating and cooling loops.

Heating / Cooling Coil

Zigzag line inside a rectangle

A spiral or serpentine device that heats or cools fluid passing through it, typically found in air handlers and fan coil units.

Pump

Circle with directional arrow

A mechanical device that uses suction or pressure to move liquids, compress gases, or force air through a system.

Heater / Cooler

Rectangle with diagonal arrows

Equipment that warms or chills water or air. Shown in vertical or horizontal orientation depending on installation.

Radiator

Solid dark rectangle

A heat-emitting device mounted on walls or baseboards that transfers thermal energy from hot water or steam to room air.

Convector

Rectangle with internal grid pattern

A finned heating unit, usually recessed or wall-mounted, that circulates warm air through natural convection.

Radiant Panel

Flat panel with wavy internal lines

A ceiling- or wall-mounted panel that provides radiant heating by warming surfaces rather than air.

Open Tank

Rectangle open at top

An unsealed storage vessel used for atmospheric-pressure water storage, expansion, or overflow collection.

Closed Tank

Sealed rectangle or cylinder

A pressurized storage vessel used in hydronic systems, domestic hot water, or compressed air applications.

Water Surface

Horizontal wavy lines

Indicates the water level inside a tank, cistern, or reservoir on plumbing section drawings.

Pipe Coil

Tight spiral or helical shape

A coiled section of pipe used to increase heat transfer area in water heaters, boilers, or heat recovery units.

Sink

Small rectangle with basin indication

A wall- or counter-mounted basin for handwashing or utility use. May include faucet notation.

Basin

Oval or semicircle at wall

A wash basin typically shown projecting from a wall line in plan view, common in restroom layouts.

Toilet

Oval attached to rectangular tank

Floor-mounted water closet shown in plan view. Wall-hung variants omit the tank symbol.

Bath

Large rectangle with rounded end

Standard bathtub shown in plan view. The rounded end typically indicates the head of the tub.

Shower Head

Circle with radiating dots

Indicates the shower spray location, typically shown on ceiling or wall-mount plumbing plans.

Towel Rail

Horizontal bar symbol

A heated or unheated rail for towels, shown on bathroom plumbing and fixture layouts.

Piping and Connection Symbols

Symbols representing pipeline types, connectors, joints, and signal lines used to show how plumbing components are linked together.

Major Pipeline

Thick solid line

A primary pipe run, typically underground, used for conveying fluid or gas over long distances between major equipment.

Connect Pipeline

Medium solid line

A secondary pipe connecting branch lines to the main run or linking fixtures to risers.

Straight Line Pipe

Thin solid line

A standard straight pipe segment shown with uniform line weight on plumbing schematics.

Process Connection

Line with directional arrow

Shows the direction of flow in a process piping system, with the arrow indicating flow movement.

Future Line

Dashed line

Indicates piping that is planned but not yet installed — used for phased construction or future build-out.

Battery Limit Line

Alternating long and short dashes

Defines the boundary between different piping systems, contractors, or areas of responsibility.

Heat Trace

Line with zigzag overlay

A system that maintains or raises pipe temperature to prevent freezing or maintain viscosity.

Electric Signal

Dashed line with wider spacing

An electric current or electromagnetic field used to transmit control data between plumbing system components.

Pneumatic Control

Double slash marks along line

Indicates a pneumatic (air-pressure) control signal line for valve actuators or instrumentation.

Hydraulic Signal Line

L-shaped line

Represents a hydraulic fluid signal or control line in process plumbing diagrams.

Sleeve Joint

C-shaped bracket

A coupling that slides over two pipe ends to form a connection, common in low-pressure drain and vent piping.

General Joint

Vertical line at pipe junction

A generic pipe connection point where two sections meet, without specifying the joining method.

Butt Weld

X mark at junction

A welded joint where two pipe ends are butted together and fused, used in high-pressure steel piping.

Welded Connection

Filled dot at junction

Indicates a permanent welded bond between pipe sections or fittings.

Mechanical Link

Oval at junction

A bolted or clamped mechanical coupling that can be disassembled for maintenance.

Soldered / Solvent

Crossed lines at junction

A joint made using solder (copper) or solvent cement (PVC/CPVC) — common in domestic plumbing.

Flange

Two parallel perpendicular lines

A bolted ring connection allowing pipes to be joined and separated. Common at equipment connections and valves.

Union

Flanged symbol with center bar

A three-piece fitting that allows a section of pipe to be removed without cutting, used near equipment.

Socket Weld

Offset parallel lines

A weld where the pipe inserts into a recessed fitting before being fused — used in small-bore high-pressure piping.

Screwed Connection

Plus sign at junction

A threaded pipe joint where male and female threads engage. Common in small-diameter gas and water lines.

Orifice Plate

Vertical lines with gap

A thin plate with a hole inserted in a pipe to measure flow rate or create a pressure drop.

Valve and Flow Control Symbols

Symbols for valves, strainers, traps, dampers, and other devices that regulate or redirect the flow of fluids in plumbing systems.

Diverter Valve

Branched arrow symbol

Redirects flow between two or more outlet paths — used in shower diverters, mixing systems, and process piping.

Y-Type Strainer

Y-shaped body with screen

Filters debris from fluid using an angled mesh screen. Installed upstream of pumps and sensitive equipment.

Y-Strainer

Oval body on pipe line

A compact inline strainer that removes particulate from water or steam before it reaches downstream components.

Blind Disc

Solid filled circle

A solid plate inserted between flanges to positively isolate a section of piping during maintenance.

Spectacle Blind

Circle-and-plate figure-eight

A rotating two-position plate — one open, one blind — that swings into place for positive pipe isolation.

Reducer

Tapered rectangle

A fitting that transitions between two different pipe diameters, available in concentric and eccentric profiles.

In-Line Mixer

Wavy lines inside pipe

A static mixing element installed in the pipe to blend chemicals, temperatures, or fluids without moving parts.

Separator

Rectangle with dividing line

Removes one phase from another (e.g., air from water, oil from condensate) in mechanical piping systems.

Bursting Disc

Dome shape on pipe

A pressure-relief safety device that ruptures at a set pressure to protect piping and vessels from overpressure.

Flame Arrestor

Grid pattern in housing

Prevents flame propagation through piping by absorbing heat through a mesh or crimped-metal element.

Drain Silencer

Elongated housing on drain

Reduces noise from high-velocity steam or gas discharge at drain and vent termination points.

Exhaust Silencer

Arrow through housing

Attenuates noise at exhaust pipe terminations for steam vents, compressors, and relief valves.

Open Vent

J-shaped pipe end

An open-ended pipe that allows air to enter or exit the drainage system, preventing trap siphonage.

Syphon Drain

U-shaped trap symbol

A drainage fitting that uses a water seal to prevent sewer gases from entering occupied spaces.

Hydrant

T-shaped post symbol

An outdoor water supply connection for fire protection or utility use, shown on site plumbing plans.

Swivel Joint

Circle with rotation arrow

Allows connected piping to rotate, used in loading arms, hose stations, and moving equipment connections.

Expansion Joint

Bellows symbol between flanges

Absorbs thermal expansion and contraction in piping runs, preventing stress on rigid connections.

Hose

Wavy line

A flexible conduit for temporary or moveable fluid connections, shown as a wavy or sinusoidal line.

Flow Indicator

Circle with directional fill

Shows the presence and direction of flow at a specific point in the piping system.

Basket Strainer

Vessel with internal screen

A removable-basket filter housing installed in piping to catch debris before it reaches pumps or equipment.

Damper

Butterfly disc in housing

Controls or shuts off flow by rotating a disc inside the pipe — used in exhaust, vent, and gas piping.

Steam Trap

Rectangle with "S" label

Automatically drains condensate from steam piping while preventing live steam from escaping the system.

Desuperheater

Rectangle with spray nozzle

Reduces steam temperature by injecting water, bringing superheated steam down to saturation temperature.

Wall, Shell, and Structure Symbols

Symbols representing walls, columns, rooms, and structural elements that appear on plumbing floor plans to show building context.

Wall

Thick solid double line

Represents a building wall in plan. Thick lines indicate exterior walls; thin lines indicate interior partitions.

Vertical Wall

Single vertical line

A wall running perpendicular to the primary plan orientation, used in simplified plumbing layouts.

Curved Wall

Arc-shaped line

A non-rectilinear wall section shown on plan — affects pipe routing and fixture placement.

Curtain Wall

Double line with horizontal marks

A non-structural glass-and-metal facade system. Plumbing rarely penetrates curtain walls but routing must avoid them.

Room Shapes

L-shape, T-shape, or rectangle with dimensions

Labeled room outlines showing area and occupancy — used to verify fixture counts meet plumbing code requirements.

Pilaster

Filled rectangle projecting from wall

A shallow column built into or against a wall, which may affect pipe routing and fixture clearances.

Rectangular Column

Filled rectangle freestanding

A structural support that plumbing must route around — identified by grid line coordinates.

Circular Column

Filled circle

A round structural column shown in plan view, requiring clearance for adjacent pipe runs.

Beam

Dashed rectangle overhead

A horizontal structural member shown with dashed lines when above the cut plane — affects overhead piping routes.

Grid Origin

Crosshair at grid intersection

The reference point where column grid lines intersect, used to dimension fixture and pipe locations.

Grid Line

Line with circle bubble at end

Part of the structural grid system. Numbers and letters in bubbles identify each grid line for coordination.

Door and Window Symbols

Symbols for doors and windows that appear on plumbing plans to show building openings, which affect pipe routing and fixture placement.

Single Door

Rectangle with quarter-circle arc

A hinged door shown with its swing arc. Plumbing fixtures and access panels must clear the door swing path.

Double Door

Two rectangles with opposing arcs

Paired doors opening in opposite directions — common at main entries and corridors.

Revolving Door

Circle with X-shaped partitions

A four-wing revolving door shown as a circle with crossed lines at building entries.

Sliding Door

Parallel lines with directional arrows

A door that travels on a track rather than swinging — does not require swing clearance from fixtures.

Folding Door

Zigzag line across opening

An accordion-style door that folds flat against the wall when opened.

Bi-Fold Door

Two angled panels

Paired panels that fold against each other — common on closets and utility spaces near plumbing walls.

Overhead Door

Dashed rectangle across opening

Roll-up or sectional garage door. Dashed lines indicate the door in the raised position.

Window

Three parallel lines in wall

Standard window shown as parallel lines within the wall thickness on plan views.

Casement Window

Rectangle with arc indicating swing

A side-hinged window that opens outward. The arc shows the swing direction and clearance needed.

Glider Window

Overlapping rectangles with arrow

A horizontally sliding window. Important to note on plumbing plans when fixtures are below windows.

Bay Window

Angled projection from wall line

A window that projects outward from the building face, creating a bump-out in the floor plan.

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