Housing plans and plumbing diagrams use plumbing symbols to represent pipes and fixtures.

You need to familiarize yourself with these symbols if you want to get plumbing upgrades approved by your local building department or want to interpret housing plans.

Plumbing Symbols: What They Mean

Plumbing symbols are used when drawing house plans and diagrams.

The purpose of these symbols is to indicate where the different elements of your plumbing system are located. Some of these symbols are self-explanatory, but others might be more difficult to interpret.

Here is what the most common symbols used in plumbing diagrams mean.

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Plumbing Pipes

Plumbing pipes are represented by different lines.

These lines will give you an idea of the plumbing layout of your home.

Figuring out the exact location of your plumbing pipes is crucial since they will impact where fixtures can go and might also have an impact on the design of your home.

Waste Pipes

Waste pipes are represented by solid lines if they are above ground.

If a waste pipe is located underground, you will use large dashes to represent it on your plumbing diagram.

Vents

You will also find lines with smaller dashes.

These lines represent vents.

These small dashes will be used to represent the main vent stack and well as smaller vents that are connected to the main stack.

Water Supply

Water supply line symbols use combinations of dashes.

You can use a large dash followed by a smaller dash to represent a cold water supply line.

A hot water line would be represented with a large dash followed by two smaller dashes. If you have a hot water return line, you will need to a large dash followed by three dots.

Fire Line

If there is a fire line on your diagram, you can represent it with large dashes interrupted by the letter F.

Gas Line

You would use the same symbol but the letter G to represent a gas line.

Other Symbols

These elements might not be present on your plumbing diagram, but it is usually helpful to know where other lines are located.

Tees And Elbows

Tees and elbows connect pipes.

The lines you draw for the pipes should represent all the turns present in your plumbing system, and you should use these plumbing symbols to indicate how the pipes are connected.

If there is a 90° elbow, draw a rounded angle to indicate how the pipe turns.

If pipes are connected with a straight tee, you will need to use a vertical line touching a horizontal one to represent the tee.

You can use this same symbol for a reducing tee, but you will need to add numbers to each pipe to indicate how the diameter of the pipes changes.

You will also need to draw P-traps on your plans or diagrams.

The line that represents the pipe should form the shape of the P-trap by dropping and going back up.

You will need to draw a fitting at the end of the P-trap.

Fittings And Valves

The plumbing symbols used to represent fittings and valves indicate whether a fitting or valve is screwed or soldered.

It is important to learn to differentiate between fittings and valves so you can choose the correct symbol.

Screwed Fittings

Here are the symbols you can use to represent screwed fittings:

A joint is a small perpendicular dash drawn across a pipe.

If there is a 90° elbow, draw a curved line and add two dashes to represent the fittings before and after the curve in the pipe.

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If there is a 45° elbow, use the same technique but adjust the curved line to represent the correct angle.

Turned-up Elbow

A turned-up elbow can be represented with a circle that has a dot inside of it. Add a small dash across the pipe next to the circle to represent the fitting.

Note that the vertical dash shouldn’t be adjacent to the circle.

Turned-down Elbow

You can represent a turned-down elbow by drawing a circle.

A portion of the pipe should be visible inside of the circle, but shouldn’t go far enough to touch the center of the circle.

There is no dot inside of the circle, and you will need to add a dash after the circle.

Double-branch Elbow

The symbol for a double-branch elbow includes lines to form the branch and a dash across the three plumbing lines.

The dashes should be placed before the intersection.

Use the same symbol to represent a tee, but make sure the lines form two 90° angles.

You can represent a tee outlet by placing a circle on the plumbing line and adding dashes on the line before and after the circle.

If there is a lateral connection, draw lines to represent the pipes and add a dash on each line before they meet.

If your plumbing layout uses soldered fittings, you will have to use small circles to represent the soldered connections.

You can use the same symbols listed above but will need to replace the small perpendicular dashes with circles.

Valves

These are the plumbing symbols you can use to represent valves:

Gate Valve

You can represent a gate valve with two triangles facing each other.

If the valve is soldered, add small circles outside of each triangle.

Globe Valves

If there are globe valves in your plumbing layout, you can use the same symbol but make sure you add a visible dot between the two triangles.

Add circles outside of the triangles if the valve is soldered.

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Tap Valves

Tap valves are represented with two triangles connected at the narrow ends and a T-shape between the triangles.

Backwater Valve

A backwater valve can be represented with a circle and a slanted line drawn across it.

Your Bathroom Layout

Your plumbing diagram might need to represent the different pipes and fixtures present in your bathroom.

Make sure you respect proportions so that the diagram shows where each fixture is located and how much clearance is around these fixtures.

Bathtub

A bathtub is usually represented by a large rectangle with a smaller rectangle inside of it. The smaller rectangle should resemble the shape of your bathtub.

Some of the corners might need to be rounded.

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Pay attention to how the rectangles are connected to the lines that represent the walls. This will indicate whether you have a corner or recessed bathtub.

Shower

If you have a shower in your bathroom, draw a double rectangle with a cross inside of it. You can represent the shower head with a half circle adjacent to the line that represents the wall, and a line to represent the pipe behind the shower head.

Lavatory

If you need to add a lavatory to your plumbing plans, you can use a double rectangle with rounded edges to represent a pedestal lavatory.

You should add another small rectangle between the lavatory and the wall if you have a wall lavatory.

Toilet

The best way to represent a toilet depends on the water closet unit you have.

You can represent a tank-type WC unit by drawing an oval for the bowl and a rectangle for the tank.

If you have a toilet with an integral tank, use a triangular shape with rounded corners.

If you have a wall-hung model, you can draw the oval portion of the bowl and add a rectangle to represent the back of the unit.

There are no standard symbols for WC units, but the shape of the symbol you use should correspond to the shape of your toilet as closely as possible.

Your Kitchen Layout

Here are the symbols you would use for your kitchen layout:

Kitchen Sink

You can represent your kitchen sink with a rectangle inside of another rectangle.

If there is a drain board next to your kitchen sink, add some horizontal lines inside of the larger rectangle.

Dishwasher

You should add appliances that will be connected to water supply lines, such as your dishwasher.

All you have to do is draw a square with the letters DW inside.

Washer & Dryer

You can use the same technique to add your washer and dryer to your plumbing layout. Draw squares with the letters W and D inside.

Radiators And Other Fixtures

Don’t forget to add radiators and other fixtures to your plumbing diagrams.

Use a single rectangle to represent radiators.

Pay attention to how the rectangle is connected to the line that represents the wall.

If you have enclosed radiators, draw a rectangle with a smaller rectangle inside.

The smaller rectangle should be drawn with dotted lines.

Your water heater can be represented with a circle and the letters WH inside.

Draw a circle with the letters HWT inside for your hot water tank.

Your thermostat is represented by a circle with T inside.

If there is a pump in your plumbing diagram, draw a triangle inside of a circle.

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Water Meter

Your water meter is a circle with the letter M underneath.

Garage Drain

You can represent a garage drain with a circle inside of a rectangle.

Roof Sump

Draw a rectangle with a double circle inside of it to represent the roof sump.

Drain

If you need to add a drain to your plumbing diagram, draw a rectangle with a D underneath.

Closing Thoughts

These are the main plumbing symbols you are likely to encounter while looking at plans and diagrams.

Don’t hesitate to double check the symbols you are using for your diagrams and plans since they need to be accurate for your local building department to approve your plumbing repairs or upgrades.

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