Plumbing systems - symbols of elements, GOST 21.205-2016

Plumbing systems are a type of engineering systems that include water supply, sewerage, heating, ventilation, air conditioning, and gas supply.

GOST 21.205-2016 establishes the basic graphic designations of elements of engineering support systems, thermomechanical and other pipeline systems, as well as alphanumeric designations of pipelines of these systems in drawings and diagrams when designing buildings and structures for various purposes.

Pipeline symbols

At the design stage of buildings, enterprises and structures for various purposes, pipelines and their individual elements are depicted on construction drawings, diagrams of thermomechanical and technological solutions, networks and engineering support systems (heating, sewerage, cold and hot water supply, gas supply, ventilation and air conditioning) using graphic symbols and simplified graphic images. They are established by the state standard GOST 21.206 - 2012.

According to the standard, the symbol of a pipeline system must have two main components:

• Simplified image or graphic symbol

• Numeric or alphanumeric designation

A digital or alphanumeric designation characterizes parameters such as the type of transported medium or the type of utility network (system), as well as the parameters of the pipeline and its purpose.

The first digit or first letter of the alphanumeric designation indicates the type of transported medium. The numbers that follow are used to indicate the parameters of the transported medium and/or the purpose of the pipeline system.

Alphanumeric designations used to designate certain types of pipeline systems used as components of engineering and technical support for buildings and structures, as well as their elements, are adopted in accordance with GOST 21.205 - 93.

To depict pipeline systems in diagrams, a conventional graphic symbol representing one line is used.

To depict pipeline systems and their individual elements in the drawings, simplified images and/or graphic symbols are used. If the diameters of the pipelines on the scale accepted for drawing up the drawing are two or more millimeters, then they are simplified by two lines.

Pipelines can be depicted with two lines without drawing a center line. It is also possible to draw a center line on a short section of the pipeline system.

To depict pipelines in electronic three-dimensional models (3D models), their diameters are depicted using two lines.

To depict visible sections of those pipelines that are being designed, a solid thin line or a dashed thin line are used, respectively.

If the pipeline is depicted as a single line in the diagram (drawing), then digital or alphanumeric designations are indicated in one of the following ways:

Symbols of pipelines in the drawings

• Leader lines on the shelf

• Above the line

• In a pipeline line rupture

Graphic representation of pipelines

If a simplified graphic representation of the pipeline is made in two lines, then digital and alphanumeric designations are indicated either directly above the graphic representation of the pipeline system, or on the shelves of leader lines.

When drawing up drawings that include pipeline systems, it is necessary to strive to ensure that the number of digital and alphanumeric symbols on the lines used to depict them is minimal, but such that this drawing (or diagram) can be easily understood.

Designation of pipeline diameters

To indicate the dimensions of pipeline diameters, as well as simplified graphic images and symbols, units of measurement such as millimeters are used. In this case, the designation of the unit of measurement itself is not indicated, and the dimensions are given either directly above the graphic image of the pipeline system, or on the shelves of the leader lines as follows:

• The symbol “DN” or the sign “Ø” is given to indicate the nominal diameter of the pipeline system before the dimensional number;

• The sign “Ø” when indicating the wall thickness of the pipeline system and its outer diameter is placed before the dimensional number;

• The symbol “DN” when indicating the nominal diameters of pipeline elements is given before the size number.

Indication of the nominal diameter depending on the type of pipe

When indicating the nominal diameter for pipeline fittings, everything is extremely simple. The rounded internal diameter is indicated, for example, like this: DN20, but sometimes an outdated designation can be found: DN20, or Dy20, according to the previously valid CMEA 254-76.

But with the indication for different types of metal and plastic pipes, not everything is so simple, and confusion often occurs due to incorrect indication or uncertainty as to what diameter is indicated, external or internal (nominal diameter).

And the question arises, how is the pipe diameter correctly indicated? The following are examples of correct designations for some types of pipelines.

Designation of water and gas pipe (VGP pipe)

Water and gas pipes (WGP) include metal welded products made of steel in accordance with GOST 1050 and GOST 380, as well as other approved regulations. Applicable:

• In building heating systems;
• Various types of water pipelines;
• In the designs of gas pipeline systems and gas pipelines;

Example notation

Steel pipe manufactured in accordance with GOST 3262-75, with a nominal bore of 32 millimeters and a wall thickness of 3.2 millimeters.

The same thing only with the clutch.

Steel VGP with thread, zinc coating, cut to length. And so on.

Designation of electric-welded straight-seam pipes

Straight-seam electric welded steels are made from low-alloy or carbon steels. Used for the manufacture of pipelines for various applications.

Example notation

Steel pipe, produced in accordance with GOST 10704-91, with an outer diameter of 70.0 millimeters, a wall thickness of 4.0 millimeters, measured length (5000 mm), class II (manufacturing accuracy along the length), made of steel “StZsp”, produced in accordance with group “B” of GOST 10705- 80.

Specifying the diameter of seamless steel pipes

Seamless steel pipes are made from alloy or carbon steels. The absence of seams increases the resistance of the pipeline to various physical influences, such as operating temperature and nominal pressure.

Example notation

Steel pipe produced in accordance with GOST 32528-2013, with an outer diameter of 60.0 millimeters, a wall thickness of 4.0 millimeters, measured length (6000 mm), increased manufacturing accuracy, grade 40X steel, produced according to group “B”.

Unmeasured length, produced in accordance with GOST 32528-2013, with an outer diameter of 95.0 millimeters and an internal diameter of 76.0 millimeters, steel grade 10, produced according to group “B”.

Indication of plastic pipe diameters

Plastic pipes and various fittings are made from the following types of thermoplastics:

They are used for the manufacture of heating pipes, hot and cold water pipelines in accordance with GOST 32415-2013.

Example of designation of plastic pipes and fittings

Manufactured from uPVC, with a nominal outside diameter of 25.0 millimeters, a nominal wall thickness of 2.3 millimeters, and a pressure rating of PN25.

Symbol for plastic fittings:

Coupling made of PVC-U for connecting pipelines with DN 63.0 mm, complies with SDR 13.6, nominal design pressure PN16.

Conventional graphic symbols of elements of plumbing systems

The symbols of general purpose pipeline elements used in the diagrams are given in the following table:

1) Filter
2) Heater
3) Cooler
4) Cooler and heater (thermostat)
5) Heat exchanger
6) Air dryer
7) Humidifier
Steam trap (condensation trap)
9) Selective device (designation shown on the pipeline) for installing an instrument

The symbols given in paragraphs 1-8 are not used in the diagrams of ventilation and air conditioning systems.

Conventional graphic symbols of tanks and pumps in the diagrams:

Conventional graphic symbols of elements of internal water supply and sewerage systems are given in the following table:

Name	In top views and plans	In front or side views, in sections and in diagrams
1) Sink
2) Washing
3) Washbasin
4) Corner washbasin
5) Group washbasin. The number of “+” signs must correspond to the actual number of taps.
6) Round group washbasin
7) Bath
Foot bath
9) Shower tray
10) Bidet
11) Toilet
12) Floor bowl
13) Wall urinal
14) Floor urinal
15) Sick leave drain
16) Gangway
17) Drain funnel
18) Internal drain funnel
19) Shower mesh
20) Drinking fountain
21) Soda fountain
22) Electric instantaneous water heater
23) Electric storage water heater

Conventional graphic symbols of pipelines and their elements:

For positions 4, 5, 6, designations of elements may be depicted in accordance with their actual configuration.

Conventional graphic symbols for the direction of flow of liquid, gas, regulation, and drive elements used in the diagrams are given in the following table:

Conventional graphic symbols of the main pipeline fittings:

1a) Gate valve through passage
1b) Angle shut-off valve
2) Three-way valve
3) Diaphragm valve
4a) Regulating valve through passage
4b) Angle control valve
4c) Triple control valve
5a) Check valve through passage (the movement of the working medium through the valve should be directed from the white triangle to the black one)
5b) Angle check valve
6a) Safety valve through passage
6b) Angle safety valve
7) Throttle valve
Pressure-reducing valve (the top of the triangle should be directed towards high pressure)
9a) Temperature control valve through passage
9b) Thermostatic mixing valve
10) Gate valve (general designation)
11) Hose valve
12) Disk valve
13a) Plug valve through passage
13b) Corner plug valve
14) Three-way plug valve
15) Four-way valve
16) Ball valve
17) Three-way ball valve
18) Automatic air vent
19) Manual radiator air vent
20) Water tap
21) Urinal tap
22) Fire cock (valve)
23) Watering tap
24) Double adjustment valve
25a) Mixer - general designation
25b) Mixer with swivel spout
25c) Mixer with shower net
25g) Bidet mixer
26) Water meter (water meter)
27) Flow meter, general designation

Additional symbols of valves by type of drive and control are given in the following table:

Additional symbols of fittings by type of action in the event of a power outage:

Conventional graphic designations of elements of heating systems are given in the following table:

Symbols for air distribution devices:

The symbols of air ducts and their elements are given in the following table:

1a) Rigid oval air duct
1b) Rigid round air duct
1c) Rigid rectangular air duct
2a) Rigid air duct with external thermal insulation
2b) Rigid air duct with internal thermal insulation
3a) Rigid air duct with external acoustic insulation
3b) Rigid air duct with internal acoustic insulation
4) The air duct is flexible
5) Elbow (bend) 90°, 45°, 135°
6) Branching, flow division
7) The transition is sharp
The transition is smooth
9) Damper (valve)
10) The damper is sealed
11) Stream switch
12) Check valve
13) Pressure relief valve
14) Smoke valve
15) Fire damper
16) Fire and smoke exhaust valve
17) Constant flow control valve
18) Variable flow control valve
19) Bypass
20) Fan (general designation)
21) Radial fan
22) Axial fan
23) Air filter
24) Multi-leaf louver valve
25) Grille (blinds)
26) Flow straightener
27) Silencer
28) Gate valve (gate)
29) Hatch for measuring air parameters and/or cleaning air ducts
30) Deflector
31) Umbrella

Symbols for air purification (preparation) devices:

1) Air mixer with constant flow (flow)
2) Air mixer with adjustable flow (flow)
3) Air heater
4) Air cooler
5) Humidifier
6) Mixing chamber
7) Fan coil
Ejection closer

Simplified images of ducts and ducts are shown in the following table: