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Main waste water collector
for the sewage of the city of Kiel

Sewage or drainage pipes are used for draining buildings or paved surfaces. In the German-speaking world, pipes made of plastic or cast iron are used in the home, less often made of stainless steel , fiber cement , glass fiber reinforced plastic or glass. In addition to plastic pipes, concrete and ceramic pipes are also used in public areas. Downpipes are also made from galvanized sheet steel.

Public sewer system

The pipeline network is the sewer network of a city or municipality for the drainage of settlement areas in a mixed or separated system . The mixed system has a common channel for rainwater and sewage , while the separating system has separate channels for rainwater and sewage.

A connection channel is a line from the public street sewer to the property line or to the first cleaning shaft in the property. In Germany, the nominal diameter DN min (= pipe diameter) is at least 15 cm.

Building drainage

Connection lines run between the drains or from the odor traps (siphons) of the individual drainage objects (e.g. washbasin , bathtub, etc.) and the connection to a fall, ground or collecting line or to a waste water lifting system .

If there is a floor drain that has inlet openings, individual drainage objects can also be connected to this via connecting lines. This has the advantage that the sealing water is renewed more often and the siphon of rarely used floor drains does not dry out.

A connection line is usually connected to a collecting line using a T-piece with a 45 ° branch. The T-piece should neither lie flat, nor should the branch point straight up; A branch inclined at an angle of 30 ° to 45 ° is preferable. The branch may only stand vertically upwards in the case of collecting pipes with a diameter of at least 100 mm and a calculated discharge from the connection pipe of less than 1 l / s. If the branch is to lie flat, a special T-piece with an eccentric branch must be used so that the bottom of all pipelines is at the same height.

Individual connection lines are connection lines that are only connected to a single drainage object and run from its drain or odor trap (siphon) to the first T-piece where two connection lines meet, or to the direct connection to a downpipe, ground or manifold.

Collective connection lines receive the wastewater from several individual connection lines and flow into a downpipe, collection or underground pipe.

Downpipes (downcomers) are perpendicular to or vented to an inclination of 45 ° installed cables, which run through one or several floors (inside or outside a building) on the roof and out the waste water of a base or manifold.

Connection and collecting pipes are usually connected to the downpipe at an 87 ° angle. If a connection or collecting line with (approximately) the same diameter is connected at a 45 ° angle, a "water bell" can form in the downpipe when larger amounts of water flow in, which negatively affects the pressure conditions in the pipe. By using 87 ° connections with rounded or beveled inner edges, the maximum drainage capacity of the pipe system can be increased.

It is important to ensure that below the discharge of faecal sewage into a downpipe, further discharges are not positioned where the sewage stream meets the inside of the pipe at an angle. This also applies below the deflections of the downpipe. Otherwise, over time, the impact of the water can cause deposits to accumulate even on the obtuse-angled edges of 45 ° T-pieces and lead to blockages of the confluent pipe.

Frequently, after a deflection, the water flow first hits the opposite side of the pipe and from there is directed back to the other side before an even, vertical outflow is established along the pipe wall. A sufficient distance should therefore either be maintained or the junction should be positioned at a point not affected by the flow of liquid.

At the transition from the downpipe to the main or collecting pipe, two 45 ° bends should always be used instead of a 90 ° bend in order to avoid blockages and strong noise. In the case of a downpipe over 10 m long, DIN 1986-100 in Chapter 6.2.2 also requires a 250 mm long, straight intermediate piece inserted between the two 45 ° bends.

A collecting pipe is an exposed, horizontal pipe to receive the waste water from downpipes.

Ground pipes are horizontal pipes laid in the ground on a plot of land or in the building, which feed the wastewater to the connecting sewer. DIN 1986-100 5.7: “For reasons of inspectability and the possibility of simple renovation , underground lines within buildings should be avoided and instead laid as collecting lines. This does not only apply to buildings without a basement ; here the ground lines should be led out of the building area as short and straight as possible. In the case of drainage systems located below the backflow level with a connection to a sewage lifting system or a backflow stop , basic pipes should only be established if connection to a collecting pipe is not possible (e.g. floor drains, showers, bathtubs). "

In Germany, underground pipes outside of buildings should be laid at a depth of at least 80 cm, as this depth is considered frost-free in the lowlands (in higher elevations the frost line can drop to 1.6 m). Changes in direction and horizontal branches are to be made at an angle of no more than 45 ° (some municipal drainage statutes require 30 °). In contrast, duct connections are usually made at an angle of 90 ° to the duct axis.

The dimensioning of underground lines is based on the relevant standards. Below buildings one speaks of building drainage and DIN EN 12056 must be applied. Outside of buildings, DIN EN 752 is the set of rules for property drainage. To dimension the underground line, DIN 1986 - Part 100 is used for both areas (below and outside of buildings). The interface between a building's drainage system and the municipal sewer network is usually the property boundary. For better operation of the public sewer, however, the municipality usually specifies the dimensions in which the inspection shaft is to be integrated into the public sewer network. The minimum size is DN150. The dimension of the underground line to the inspection shaft is calculated hydraulically by a specialist planner. This applies both to lines below a building and outside of a building. The minimum diameter (DN min ) is usually 100 mm, if the calculation allows it, 90, 80 and in individual cases even 70 mm are possible. Overdimensioning should be avoided at all costs in order to guarantee the self-cleaning of the underground pipe. One- and two-family houses should always be connected to the inspection shaft with basic pipes of nominal width DN100 with the usual sanitary facilities. There is often a mix-up in the designation of the pipe sections, so that the underground pipes are expanded to larger nominal widths before the inspection shaft, in some cases even to a nominal diameter of DN150 in single-family houses.

Cross-sectional constrictions are to be avoided in principle. Cross-section expansions are to be aligned so that the top of the pipe is at the same height. Basic lines are an exception. Here, the bottom of the pipe should run through without a change in height so as not to hinder the tracking shot in the event of an inspection.

A rectangular cleaning opening or a shaft with an open flow should be provided for underground pipes in the immediate vicinity of a change in direction .

Table 1 of DIN EN 1986-4 lists the line materials to be used for inaccessible lines such as underground lines.

Gradient, flow velocity

DIN 1986 previously required a gradient of at least 2% for DN-100, 1.5% for DN-150 and 1% for DN-200 pipes (always 1% for rainwater). According to DIN EN 12056 and the newer DIN 1986-100, 0.5% (0.5 cm / m) is sufficient in most cases for ventilated and 1% (1 cm / m) for unventilated lines.

For underground pipes from DN 250 upwards, the minimum gradient in percent corresponds to the reciprocal of the nominal width (J = 100 / DN). Outside of buildings or with mixed water pipes, according to DIN 1986-100, this also applies to pipes with a smaller cross-section.

According to EN 752, collecting and underground lines should not be laid with a bottom slope of between 5% and 100% (corresponds to 3 ° to 45 °), as in this area there is a risk that solids will separate from the liquid due to the high flow rate and what will remain Material adheres to the pipe wall. In contrast, with the recommended gradient of between 0.5% and 2% (for pipes with a nominal diameter of 200 mm or more) or up to 5% (for pipes up to 150 mm nominal diameter) , solids are carried away by the liquid. Larger differences in height should be bridged by a stepped pipe run (if possible with control and cleaning openings) or by a so-called fall within a shaft.

Some manufacturers of wastewater lifting systems recommend a minimum gradient of 2% in the inlet.

Horizontal drainage pipes with free-fall drainage / gravity drainage

A gravity drainage or gravity drainage is a gravity drainage. Both terms are mostly used synonymously .

Gravity lines are operated partially filled, i.e. the degree of filling of a gravity line is usually less than 1 (filling height h / inner pipe diameter d i ).

In Germany, an average fill level of 0.7 in the sewage pipes is planned. (A degree of filling h / d i of 1.0 is permissible behind the connection of a lifting system .) The flow velocity v should be between 0.7 m / s and 2.5 m / s.

In order to safely transport feces away, a certain flooding depth is required, which is measured according to the calculated filling level of the pipe. The degree of filling corresponds to the ratio of the water depth (h) in the current to the pipe inner diameter (di). The flushing of the faeces is usually guaranteed if the degree of filling h / di is 0.5. During the drainage process, the pipe is then half filled with water.

Pressure drainage

The filling level of an (over-) pressure line is usually approximately 1 (filling height h / inner pipe diameter d i ).

Drainage via pressure pipes occurs when lifting systems or other pumps are used to transport the wastewater, as well as gravity drainage without the use of auxiliary energy

In Table 1, DIN EN 1986-4 limits the materials to be used for pressure pipes to cast pressure pipes, PP pressure pipes with welded joints (DIN 8077; DIN 8078; DVGW W 544), PE pressure pipes, PVC pressure pipes and stainless steel pressure pipes.


In contrast to the other line types, connection lines can also be designed for full filling and operated in this way. However, they must not contain more than three 90 ° bends. A non-ventilated connection line may be a maximum of 4 m long and must have a gradient of at least 1%. The height between the odor trap and the opening in the downpipe must not be more than 1 m. If these conditions cannot be met, a pipe ventilator must be provided immediately behind the odor trap. A ventilated connection line can be up to 10 m long and must be laid with a gradient of at least 0.5%. The height between the odor trap and the mouth in the downpipe must not be more than 3 m.

If the connection line cannot be connected to a ventilation line running over the roof, the occurrence of negative pressure in the pipe can be avoided by using a ventilation valve. The manufacturer sometimes sets further requirements. In some cases, the valve should sit above the connection pipe on a vertical piece of pipe at least 10 cm long (15 cm for toilet drains). It should be no more than 1 m lower than the upper edge of the nearest sanitary object (washbasin, shower tray, etc.) and not more than 1.5 m away from it. It should be installed vertically and not covered. Access for maintenance and an influx of air must be possible and it must be insulated against frost.


Typical pipe diameters of individual connection lines:

  • Wash basin (DIN 1986-100, Tab. 6; connected load DU 0.5), washing machine and dishwasher DN 40. With long pipe lengths and poor accessibility, under certain circumstances DN 50.
  • Bathtub, shower (DIN 1986-100, Tab. 6; connected load DU 0.6) and sink in the private sector DN 50. Exceptionally if the degree of soiling (hand washbasin) or good accessibility (short length, few bends, cleaning openings) and ventilation of the pipe are concerned also DN 40.
  • Urinal: DN 50. In the case of waterless urinals , low flush volumes or frequent use, better DN 70 or larger in order to delay the closure with urine stone.
  • WC with up to 6 liter cistern : DN 90 (DIN 1986-100, Tab. 6; connection value DU 2). Also DN 80 after calculation (in exceptional cases DN 70). From three connected toilets DN 100, each up to max. 10 m long, three 90 ° bends and 1 m height difference between the inlet and the mouth in a downpipe or alternatively in a collecting or underground pipe of larger dimensions.

In general, non-ventilated connection pipes up to and including DN 70 may only be 4 m long, contain three 90 ° bends and overcome a height difference of 1 m between the inlet and the mouth in the downpipe or, alternatively, open into a collecting or underground pipe of larger dimensions.

Hunt group line

In residential buildings and under certain circumstances in public facilities, the collective connection lines may be designed in DN 90 according to DIN 1986-100, Tab. 7, provided that the drainage capacity of the connected sanitary objects does not exceed a connection value of 13 l / s and no more than two toilets are connected are.


The nominal size of a downpipe with main ventilation is based on DIN 1986-100, Tab. 8, on the sum of the connection values ​​and the building type.

When using branches (T-pieces), the outlet of which connects to the downpipe with a certain radius, a downpipe with main ventilation in DN 90 can accommodate a wastewater discharge QWW of 3.5 l / s. If, on the other hand, the T-pieces of the outlets have sharp-edged branches, the wastewater discharge QWW should not exceed 2.7 l / s.

Due to the rounding of the connections, the incoming water follows the pipe wall. The rest of the pipe cross-section remains free, which ensures pressure equalization. In the case of sharp-edged inlets, on the other hand, it is carried by the motion impulse into the middle of the pipe before it falls down. In doing so, it can pull down the air contained in the pipe. This is disadvantageous because a negative pressure is created above and an overpressure below it.

Cleaning openings

Pipe end seals (plugs) and manholes with an open flow also count as cleaning openings.

Cleaning openings are to be provided at the transition from vertical to horizontal lines. Likewise every 20 m in underground lines and collecting lines. If there are no changes in direction, a distance of 40 to 60 m is sufficient.

Cleaning openings with rectangular or oval openings are to be provided in basic pipes.

A cleaning opening is to be provided near the property line at a maximum distance of 15 m from the public drainage canal.

Cleaning openings must not be installed in rooms in which food is processed and stored.

Laying in the ground

Lines newly laid in the ground must be checked for leaks in accordance with the guidelines of DIN EN 1610. The test can be carried out with air or water as the test medium.

Wall penetrations

Sealing of the building connection

DIN EN 12056 and DIN 1986-100 call for drainage pipes to be carried out underground in outer walls to be watertight and gas-tight. This can be done, for example, by pushing a wall collar over the pipe , which is poured into the wall with concrete.

DIN 18195 describes different types of sealing and specifies requirements for the production of the penetrations.


Settlement of the structure or the filling material often occurs with new buildings and after backfilling .

In order to avoid damage to the drainage line in accordance with DIN EN 12056 and DIN 1986-100, the pipe in the area of ​​the building entry should be covered with a soft material, e.g. B. insulation, be sheathed. The length of the jacket should correspond to the pipe length for which an influence from the settlement movement is assumed. To determine the outer diameter of the pipe is added to the value of the expected settlement, in each case in centimeters. The root is taken from the sum and the result is increased tenfold. The casing should be partly in the wall and partly in the ground.

Pipe systems

  • HT pipes (high temperature pipes): They are mostly gray in color and are usually used inside buildings. In the ground, the thick-walled KG pipes are preferred.
  • PE pipes : These black pipes are or can be used within a building and as ground pipes.
    Connection technology : mirror welding, electric welding or push-in sleeves.
  • Sound-insulating plastic pipes are usually made of polyethylene (PE) or polypropylene (PP). The emission of airborne sound is usually reduced by increasing the wall thickness and increasing the density of the base material by adding mineral fillers.
  • KG pipes (sewer base pipes): They are usually made of PVC , mostly colored orange, more stable than HT pipes and are mainly used as base pipes. Since they are less impact-resistant and temperature-resistant, they should not be used for exposed downpipes or collecting pipes.
  • KG2000 pipes (sewer base pipe 2000): They are usually made of PP , often colored green or white, more stable than KG pipes and are used as base pipes.
  • GRP pipes (glass fiber plastic pipes): These pipes generally have d. Usually high stability and can also be used in chemical areas.

Plastic pipes are subject to higher thermal expansion than pipes made of metal and ceramic or mineral materials. Pipes, which are used for draining bathtubs, kitchen sinks and washing machines, for example, expand when the draining water has an elevated temperature. In order to avoid constriction and bending of the pipe, the spigot ends in pipe strings that run straight for several meters without deflection should not be pushed into the sockets as far as they will go. As a rule, it will be sufficient to give the pipe about one centimeter to expand.

  • SML pipes (Super Metallit delivery program): pipes made of gray cast iron; they have a reddish coating on the outside and are normally used as sleeveless pipes in buildings. The red SML pipe must be provided with corrosion protection for laying in the ground . The butt pipe ends are connected by means of clamping rings or claws.
  • GJS pipe (nodular cast iron pipe ), formerly GGG pipe (globular gray cast iron pipe): They are mostly colored brown; They are mainly used underground as pressure pipes or gravity sewers for the disposal of service water. They are usually galvanized and have a cement mortar (ZM) lining.
    Connection technology : Sockets with simple lip seals, claw seals and a combination of lip seal and wedges for tensile strength.
  • Stainless steel pipes : They can be used as an alternative to cast iron pipes; Can be used indoors and outdoors, easier to lay and compatible with plastic pipes.
  • Stoneware pipes: Made from mineral materials, glazed on the outside and inside, dark brown and much heavier and more expensive than plastic pipes. For a long time, at least until the 1960s, they were the standard for underground pipes. Today, because of their high static load capacity, they are preferred when there is high ground pressure (such as under roads).
    Today the spigot ends of the pipes usually have molded rubber rings. In the past, solid or profiled sealing rings were inserted into the sleeves. Until the 1960s, tarred hemp packs were stuffed into the socket crevices, which were then covered with cement mortar.
  • Concrete pipes: Reinforced or unreinforced, use as underground pipe, inexpensive pipe bedding in gravel 0/32 mm or concrete base.
    Connection technology : Sleeves with rubber seal (sealing ring).

According to DIN 1986-4, pipes made of the following materials are unrestrictedly resistant to acid condensate , which is created and must be removed when operating gas or petroleum-operated condensing boilers : stoneware, glass, polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP ), Styrene copolymers (ABS / ASA), polyester resin (UP) and stainless steel. If diluted by other wastewater , pipes made of fiber cement, cast iron or steel can also be used.

DIN standards and EN standards

The following European standards (EN) or DIN standards are related to drainage:

  • DIN EN 1610: Laying and testing of sewer pipes and sewers; German version EN 1610: 1997
  • DIN EN 1610 - Supplement 1: Laying and testing of sewers and sewers - List of relevant standards and guidelines (as of February 1997)
  • DIN 1986-3, -4, -30 and -100 : Drainage systems for buildings and properties.
    • DIN 1986-3: Drainage systems for buildings and properties - Part 3: Rules for operation and maintenance
    • DIN 1986-4: Drainage systems for buildings and properties - Part 4: Areas of application of sewage pipes and fittings made of different materials
    • DIN 1986-30: Drainage systems for buildings and properties - Part 30: Maintenance
    • DIN 1986-100: Drainage systems for buildings and properties - Part 100: Additional provisions to DIN EN 752 and DIN EN 12056
  • EN 752: Drainage systems outside of buildings
    • DIN EN 752-1: Drainage systems outside of buildings - Part 1: General information and definitions; German version EN 752-1: 199
    • DIN EN 752-2: Drainage systems outside of buildings - Part 2: Requirements; German version EN 752-2: 199
    • DIN EN 752-3: Drainage systems outside of buildings - Part 3: Planning; German version EN 752-3: 1996
    • DIN EN 752-4: Drainage systems outside of buildings - Part 4: Hydraulic calculation and environmental protection aspects; German version EN 752-4: 1997
    • DIN EN 752-5: Drainage systems outside of buildings - Part 5: Renovation; German version EN 752-5: 1997
    • DIN EN 752-6: Drainage systems outside of buildings - Part 6: Pump systems; German version EN 752-6: 1998
    • DIN EN 752-7: Drainage systems outside of buildings - Part 7: Operation and maintenance; German version EN 752-7: 1998
  • EN 12056-1 to -5: Gravity drainage systems inside buildings:
    • DIN EN 12056-1: Gravity drainage systems inside buildings - Part 1: General and design requirements; German version EN 12056-1: 2000
    • DIN EN 12056-2: Gravity drainage systems inside buildings - Part 2: Wastewater systems, planning and calculation; German version EN 12056-2: 2000
    • DIN EN 12056-3: Gravity drainage systems inside buildings - Part 3: Roof drainage, planning and dimensioning; German version EN 12056-3: 2000
    • DIN EN 12056-4: Gravity drainage systems inside buildings - Part 4: Wastewater lifting systems; Planning and dimensioning; German version EN 12056-4: 200
    • DIN EN 12056-5: Gravity drainage systems inside buildings - Part 5: Installation and testing, instructions for operation, maintenance and use; German version EN 12056-5: 2000

See also

Individual evidence

  1. Jörg Probst: Drainage planning ( Memento of the original from February 18, 2018 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) p. 6. Bochum University of Applied Sciences - Department of Architecture, as of 2010. @1@ 2Template: Webachiv / IABot /
  2. a b wastewater hydraulics. Guidelines for planning, dimensioning, implementation (PDF) Geberit Vertriebs GmbH, 2017.
  3. Information on sewage systems , Akatherm; accessed in February 2017.
  4. a b c d e Bruno Bosy: Installation dimensions - sanitary heating - ventilation , In:; accessed in April 2019
  5. "Instructions for installation, operation and maintenance" for the Aqualift F boiler waste water station for installation in the base plate for waste water containing faeces, CE approval Z-53.2-484. Change status May 2011.
  6. Philipp Claus: Expert Advisory Committee on Ground Lines - Quo Vadis Sewage Systems: New Challenges for an Old Topic, Geberit Vertriebs GmbH, Pfullendorf, July 2012.
  7. a b c d e f g Peter Reichert: Wastewater pipes in buildings are often oversized - a lot doesn't always help a lot , Product Management Pipeline Systems Geberit GmbH, BTGA Almanach 2014, p. 40ff; In:
  8. a b c d e Construction site instruction PE ( Memento of the original from January 17, 2018 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) Geberit, 2017. @1@ 2Template: Webachiv / IABot /
  9. Frank Sprenger: Condensation water from boilers and its neutralization (PDF) special edition Buderus Heiztechnik.