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A valve ( Latin armare "equip") in sanitary engineering and plant engineering designates a component for changing and controlling material flows , which is used in particular on pipelines and containers ( boilers ) for gases and liquids.

A mixing valve usually has three or four inputs and outputs (three or four-way valve) and is used for the controlled mixing of material flows.


Gate valve
Shut-off valve for heating return.jpg
Gate valve in the heating circuit

Shut-off devices

Valves cause a cross-section reduction or the closure of a pipeline by a closure body moving axially towards a correspondingly shaped sealing seat. This movement is either controlled externally or it happens automatically, as is the case with a check valve , which prevents flow when the direction of flow is reversed.

In the domestic sector, poppet valves have traditionally been used as outlet valves , in which the flow opening is closed by a flat or conical valve disk. Modern single-lever mixers regulate the flow through sliding ceramic discs.

Butterfly valves control the flow through flaps that are rotatably mounted on an axis lying in the flap plane.

Gate valves contain a locking disk that can be displaced transversely to the direction of flow, piston valves contain adisplaceable piston.

A cock has a cylinder with a transverse through-hole or an elongated cone with a bore, which are arranged to be rotatable about the longitudinal axis at right angles to the direction of flow. If the hole is perpendicular to the direction of flow, the valve locks. By turning the cylinder or cone, the bore is aligned in the direction of the material flow and the valve opens.

Ball valves have a pierced ball instead of a cylinder or cone.

The manually operated shut-off and control valves include:

Fittings under a spherical gas container

In contrast, non-return valves , check valves , backflow preventer , ball valves and KFR valves automatically operate and allow the medium to pass in one direction only.

Automatically operating valves with special tasks are:

Valves for special applications:

In a broader sense, other internals in pipelines are also referred to as fittings. For example:

The connection between the valve and the pipelines is traditionally made by means of a screw connection or a detachable screw connection using a union nut and metallic or flat seal. Fittings that are intended for crimp, clamp or plug connections are also increasingly being offered. Flange connections are also used if there are special requirements and if there are larger pipe diameters .

The overall length of fittings varies greatly. For Europe, overall lengths are defined in EN 558-1. Typical overall lengths for gate valves are, for example, the basic series 14 and 15.

Outlet fittings

Household drain fittings are traditionally known colloquially as faucets . Combined hot and cold water outlet valves are available as single-lever or two-handle fittings and are often called mixer taps .

Typical flow rates

  • Kitchen faucet in the household: 4 to 6 liters of water per minute (regardless of the water pressure)
  • Kitchen faucet with additional function for increased flow ("Boost function"): if necessary, temporarily up to 8 liters of water per minute
  • Device connection fitting (for dishwasher or washing machine): up to 15 l / min
  • Basin mixer with rotary handle: 3.5 to 6 l / min
  • Shower and bath filler: 9 l / min
  • Toilet cisterns: When the siphon bell is triggered, 6 liters of water flow once in modern systems, traditionally 9 liters. With a dual flush, the flow rate can be limited to 3 liters.

The flow rate of the filling valve ( float valve ) is usually between 4 and 12 liters per minute (0.05 and 0.2 l / s; according to DIN 19542 and DIN 1988-300 Table 2, the calculated flow rate is 0.13 l / s at 0.5 bar minimum flow pressure and DN 15).

Self-closing valve

  • Sanitary fittings with a running time limit should automatically stop the flow after 10-15 seconds.
  • Sensor fittings only open as long as the sensor is activated or after a maximum follow-up time of one second.
  • WC flush valves usually close after running for 9 seconds
  • Urinal flush valves close after around 3 seconds.

Areas of application

Each valve has its area of ​​application according to the prevailing pressure and temperature in the pipeline , the size of the pipeline, the tightness requirements of the valve, the throttling and the direction of the fluid flow as well as the medium itself.

Specially sealed fittings, so-called gas taps, which are adapted to the gas pressure, are installed in domestic gas pipes; Appropriate shut-off valves or throttle valves in water pipes, which are colloquially called "water taps".

Safety / safety fittings in drinking water installations

Safety fittings according to DIN EN 806-1 or DIN 3211 are control devices to prevent dangerous physical operating conditions such as excessively high pressures or temperatures:

A safety fitting in accordance with DIN EN 806-1 protects the quality of the drinking water by preventing process water from flowing back into the pipe network. They include non-return valve , pipe separator , vacuum breaker , backflow preventer and pipe ventilator .


An initial shut-off is a valve that enables the separation of a branching pipe line in a pipeline network. The main shut-off device (HAE) of the house connection is located near the house entry for the supply lines .

Control valves

Pressure reducers reduce the flow pressure in a pipe system, mostly to protect sensitive system components from pressure surges and fluctuations.

Line regulating valves help with the hydraulic balancing of pipe systems with several lines, all of which are to be supplied with a defined volume flow. In order to generate the lowest possible pressure drop, (shut-off) valves , piston valves , (shut-off) flaps and angle seat valves are ideal for this task . Ball and plug valves would be suitable, but do not allow precise regulation of the volume flow.

Differential pressure relief valves protect uncontrolled pumps and boilers from insufficient flow by opening a bypass line if the pressure in the main pipe increases too much.


Can fittings manually by hand , as with domestic tap , through the use of air pressure ( pneumatic ), or fluid pressure ( hydraulic ) and electrically via magnets or motors are operated. In the case of check valves , the fluid flow in the pipeline causes the valve to close automatically.


The valve body is often designed as a cast construction and made of gunmetal , as this material is easy to process and largely corrosion-resistant, does not promote bacterial growth and does not become brittle at low temperatures. Gunmetal is similar in its alloy composition to bronze .

Simple valve bodies can be manufactured as a machining construction and are often made of brass . Brass is stronger than gunmetal, but less resistant.

In the home, fittings made of brass or gunmetal are often chrome-plated or nickel-plated.

Larger fittings for industrial use are also made of cast steel and are protected against corrosion with a coating of epoxy resin or enamel .

Valves made of stainless steel and plastics (e.g. hard PVC ) are also used with corrosive media .


The nominal size is marked with the abbreviation "DN". In the case of fittings with an imperial thread connection , the imperial dimensions that were customary in the past are also given.

The flow  resistance of the valve cannot necessarily be deduced from the nominal size . Fittings of the same size that look similar can also have free cross-sections that differ greatly from one another. The exact values ​​can only be found in the manufacturer's documentation. With taps and gate valves, the free cross-section can often be assessed and measured in the open position. Due to the diversion of the material flow, this is not possible with valves.

Marking and abbreviations

Usual markings on fittings:

  • 1/4 ", 3/8", 1/2 ", 3/4", 1 ", 1 1/4", 1 1/2 "etc. - obsolete designation of the nominal width , depending on the context also the size of the connection thread
  • DN - nominal size , e.g. B. DN10, DN12, DN15, DN20, DN25, DN32, DN40, ... (order and dimensions correspond approximately to the above-mentioned inch nominal widths)
  • DVGW - approved by DVGW for use in gas and drinking water installations
  • KIWA - approved by KIWA (formerly Keuringsinstituut voor Waterleidingartikelen ), a provider of certifications and inspection services in gas, energy, drinking water and production safety
  • OV - Abbreviation of the manufacturer Oventrop
  • PN - pressure rating, d. H. permissible pressure in the typical application range, depending on the temperature and application, a higher or lower maximum pressure can result

Type of fitting:



  • Rainer Jockenhöfer (Ed.): Valves in gas and water distribution . Vulkan Verlag, Essen 1999, ISBN 3-8027-5408-5 .
  • Bernd Thier: Industrial valves - components of pipeline technology . 5th edition. Vulkan Verlag, Essen 1997, ISBN 3-8027-2712-6 .

Web links

Commons : fittings  - collection of images, videos and audio files

Individual evidence

  1. ↑ Overall lengths of fittings according to EN 558-1 (KVT GmbH)
  2. a b Bruno Bosy: Flow rate measurement. In:
  3. a b Peter Schott: Sanitary technology - safety and safety fittings in drinking water installations. In: IKZ building technology. 10/2000, p. 56 ff.
  4. ↑ Valve materials brochure . Gebr. Kemper GmbH + Co. KG - metal works
  5. ^ Abbreviations in the HVAC trade , Bruno Bosy