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Floor-flush shower channels: What is valid as a consideration with planning, selection and installation

Floor-flush shower channels: What is valid as a consideration with planning, selection and installation

A floor-flush solution for the drainage of the shower area is often the first choice when a bathroom is newly built or renovated.  A floor-flush shower channel is part of a barrier-free bathroom and in some countries can be eligible for funding – in Germany the state-owned KfW Bank provides funding. Detailed information is available at

In addition to floor evenness, there are advantages in terms of design and installation: Channels can be perfectely integrated into the floor covering; connection of compound sealing is problem-free; the height and gradient of the channel can be adapted on-site, pipe can be individually routed, and when in use floor-flush channel is simple to clean and hygienic. The prerequisites for an installation that will prove itself in everyday use are professional planning, good model selection and, of course, professional installation.

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1. Professional bathroom planning

The decisive points of professional planning are the floor structure and the floor gradient. Professional bathroom planners must observe the following standards:

  • EN 12056, Part 1 (!General and implementation requirements”) and Part 2 ("Wastewater pipes, planning and calculation”), defines the requirements for drainage systems within buildings.
  • EN 1253-1 regulates the technical implementation of sanitary appliances (including the required discharge capacity of the sanitary appliances, the use of odour traps and the load classes for gratings and covers).
  • DIN 18024 contains the provisions for age and handicapped-related accessible building
  • DIN 4109 specifies the provisions for sound insulation in public buildings such as hotels, hospitals, multi-dwelling buildings and senior citizens' houses.
  • EN 1366 and DIN 4102 regulates (additional to country-specific requirements) the requirements for fire protection in public buildings.
  • 18534 contains the rules and specifications for internal waterproofing and is therefore particularly relevant for the installation of a shower channel.

1.1. The floor structure

The development of waterproofing technology has also led to new, modern compound sealing systems in the bathroom sector. For example, the use of one-component and two-component sealant materials, which are applied by spatulas or rollers. In terms of building physics, one makes a distinction between three floor substructures with waterproofing, taking into account the water impact classes:

  • Sealing with floor covering such as PVC flooring or synthetic resin floor covering
  • Sealing with a sealing membrane or alternative compound sealing
  • Sealing with two sealing membranes (can also be a combination of conventional sealing and alternative thin-bed sealing)

It is normal to plan a bathroom with a floor structure which has liquid sealing materials. Depending on the effect of water, the shower area, the entire bathroom floor and partly also the wall area will need to be sealed.

1.2. The floor gradient

Bathroom drainage functions according to the gravity principle. In order for the water to drain off on the floor in the direction of the shower channel or floor drain, the floor must have a gradient: The relevant technical literature recommends a gradient of approx.

2%. This means that in a 100cm deep shower area, the height difference from one side to the other is 2cm. If the gradient is insufficient or non-existent, puddles will form and water will spread over the entire surface of the floor (flooding).

In addition to the gradient, the accumulation height of 20mm above the channel grating required by DIN EN 1253 and the resulting maximum discharge value must also be taken into account. If shower channels are installed as room dividers in the bathroom on the room side rather than on the wall side, it is important to ensure that water does not flow onto the floor to quickly and cause the drain to overflow.

2. The right product selection: Function and design

Whether it's a new building or a bathroom refurbishment, the shower channel or floor gully is expected to provide trouble-free and low-maintenance operation for many years, if not decades. This operation must be guaranteed by the technical functions that a modern shower channel has to fulfil:

  • Connection to compound sealing
  • Connection of standardised pipes
  • Take up and trouble-free drainage of shower water
  • Securing the bath against odours and gases from the sewage system
  • Protection against fire and smoke propagation between two fire compartments
  • Load capacity by pedestrian and/or other traffic
  • Sound protection

2.1. Connection of composite sealing

The regular water loads created in a shower area require a particularly reliable, permanent sealing of the floor structure. The new DIN 18534 is decisive with regard to the sealing of interior spaces and mainly replaces Part 5 of DIN 18195. It contains the rules and specifications for sealing or waterproofing kitchens, bathrooms, shower facilities or floor areas with drains - and is therefore of the highest relevance for the processors and planners of shower channels and floor drains. Unprofessional and/or inadequately executed sealing can cause considerable damage to the building structure. The best guarantee for a permanently watertight floor structure is a professionally executed connection of a composite seal with a connecting collar to a circumferential shower channel flange. A shower channel with a circumferential, fixed connection flange provides the possibility of securely connecting compound sealing with the aid of connection collars or sleeves. A flange width of 30mm is the minimum valid standard here.

2.2. Connection to pipe

To ensure the connection of the shower channel to the drainage system functions without any leaks, its drain connection including its dimensions must be matched to the standard waste water pipes for the shower channel area in accordance with DIN 1986 Part 4.

2.3. Water absorption and discharge

The basis for selecting a shower channel is the amount of water produced by the shower fitting. The average flow volume of shower fittings is approximately 0.15 to

0.2 l/s. In the case of larger shower panels or shower heads with a correspondingly high water flow, shower channels with several integrated drains may be required so that the volume of waste water produced is discharged with as little water accumulation as possible. Water collection is executed via the grate of the shower channel. In order to ensure that the volume of water created can also be safely discharged, the manufacturer's data regarding water backflow above the grate or cover and the associated volume of wastewater discharge must be known. In addition, the openings of the slotted gratings as well as the circumferential inlet slots must also be suitable for barefoot areas. DIN EN 1253 defines slot widths of a minimum 4mm and amaximum of 8mm for the shower area. Versions with larger slot widths can cause injuries to toes, especially for small children. Since the grate is the most visible element of a shower channel, the choice of design naturally plays a decisive role.

2.4. Odour protection

In order to protect the bathroom against penetrating odours and gases from the public sewage system, a removable odour trap with a water seal is used in modern shower channels.  This can be dismantled for cleaning purposes and allows free access to the pipe. A water storage height of 50mm is a safe and standard-compliant odour seal height according to DIN EN 1253-1. Such a water storage can safely compensate for the over-pressure and under-pressure in the downpipe. Lower odour seal heights can lead bad odours to occur more quickly in sparsely used baths than when odour traps with standardised water seal heights are used. They are regarded as deviations from standards which must be agreed with the customer in individual cases.

2.5. Fire protection

Preventive fire protection must be observed in multi-dwelling buildings including

owner-occupied flats, hotels, senior citizens residences, public buildings and hospitals. When the shower channel drain outlet socket is routed vertically through the ceiling, then shower channels with fire protection equipment are preferably used. In the event of a fire, ceiling penetrations or openings are particularly critical points through which fire and smoke can quickly spread to the next storey. Utilising a shower channel with integrated fire protection is a safe solution. The water storage in the odour trap of the shower channel (minimum 50mm) and a removable fire protection insert (fire resistance class R30 to R120) help prevent fire and smoke spreading to the next storey. The shower channel must have at least the same fire resistance class as the ceiling in which the channel is embedded.

2.6. Load capacity

Shower channels are installed in the walking area and are therefore exposed to traffic loads. The covers and/or gratings of shower channels must be tested for load in accordance with DIN EN 1253 and classified accordingly. A load capacity of shower channels according to load capacity K3 (according to DIN EN 1253-1 surfaces without traffic, loadable up to maximum 300kg) is customary on the market.

2.7 Sound protection

The requirements for the installation sound level must be complied with for sound protection. When implementing sound protection measures, it must be initially determined whether sound protection is required in accordance with DIN 4109 or

VDI 4100. DIN 4109 “Sound protection in building construction” is, according to a fundamental ruling of Germany’s Federal Court of Justice, an introduced technical building regulation which only fulfils the minimum requirements for sound protection under public law. The court ruling also states that DIN 4109 is for the most part irrelevant for civil law and is therefore only valid when agreed upon in a work contract under certain conditions. Noise levels according to today's usual standards for quality and comfort cannot be achieved with DIN 4109: The specified minimum acoustic values no longer comply with today's recognised best practice. If the values according to DIN 4109 are nevertheless required, then this must be clearly and unambiguously formulated in the works and services contract. The VDI 4100 “Sound protection on residential buildings” (primarily in the sound protection levels SSt II and SSt III) reflects the sound. The requirements for modern and comfortable living spaces and in buildings such as hotels, clinics and senior citizens residences have more stringent requirements.

2.8 Design

Design plays an important role alongside function and comfort in modern bathrooms. The design, in turn, is decisively influenced by the geometry: There is a choice of predominantly straight versions for laying along a wall. The shower channel and/or its cover as the only visible part of the channel is usually the only interruption of the often high-quality floors. The aesthetic demands on the channel are correspondingly high. Shower channels can be provided with the same tiles as the surrounding floor. With

tiled covers, the shower channel becomes almost invisible. If, on the other hand, you would like your gratings to be eye-catching, then select a design grating made of stainless steel. High-quality versions have an electro-polished, particularly smooth and thereby dirt-repellent and hygienic surface. Design covers made of single pane safety glass also harmonise particularly well with shower enclosures made of glass. In connection with light modules, such as ACO Lightline Pro, they create a particularly atmospheric effect in the bathroom. The ACO ShowerStep slope wedge is a particularly elegant solution for covering the slope edge between the shower floor and the extended bathroom area and can also serve as a base for a glass shower partition.

3. Professional installation

In practice, even the best product is only as good as the quality with which it is installed. Specialist, professional know-how is required for assembling a shower channel. In addition to the classic methods, the ACO ShowerFloor floor system has established itself as a system solution with numerous advantages: It combines maximum flexibility in every respect - surface, slope, pipework, surface/cover - with simple installation, high stability, fast workability, secure sealing and very good sound protection.

3.1. Installation in the screed

The classic method for a shower channel installation commences with the insertion of the shower channel into the floor recess provided, followed by screwing the channel supports to the raw concrete slab. Height-adjustable feet such as those incorporated into ACO ShowerDrain channel, simplify the levelling of a channel to the height of the upper edge of the surrounding floor. HT pipes DN 50 or DN 40 can usually be directly connected to the outlet socket of the channel. Care must be taken when laying the screed to ensure that the shower channel is completely grouted in without any bubbles in the grout. The compound seal connection can be executed after the screed has dried and cured. In order to avoid permanent damage, the compound seal implementation must be executed with the utmost care, taking into account the preparation and working instructions of the respective manufacturer and the relevant regulations. The tile adhesive can subsequently be applied and the ceramic tiles can be laid. It must be ensured that an expansion joint (working joint) is provided between the ceramic tiles and the frame of the shower channel, which is then elastically grouted after completion of the work using a primer. The protective film is subsequently removed from the shower channel and the grate and/or cover can be inserted.

3.2. Installation with floor system

The only prerequisite for the installation of a floor-flush shower channel with the ACO ShowerFloor floor system is a solid substrate. The speed of the installation is based on the basic structure of the system: A beam and/or frame made of steel profiles with three or four parallel cross struts for linear drainage or two crossed diagonal and cross struts for each for point drainage. Robust plug-in connections mean the entire frame can be sized quickly by simply sawing the individual profiles to the required length. The feet compensate for any unevenness on site and, due to their flexible positioning possibilities, provide the necessary clearance for the pipe routing. The height adjustment and also the precise and simple adjustment of floor level and gradient is executed with just four adjustment feet in the four corners of the shower area. All other stand feet can be adjusted with a click lock (similar to a photo tripod) in basically just one manual action.

The installation of the shower channel is thereby reduced to just a few simple steps that can be executed in one single operation:

  • Assembling the feet
  • Placing the complete carrier frame in its position
  • Adjusting the positions and height of the feet
  • Placing the drainage element, connect it and check for leak tightness
  • Placing the support plate on the surface and adhering it

At this point, the single switch over of the trades can be executed and the tiler can  begin the sealing work. The single switch over of the trades reduces downtime and increases planning reliability. ACO ShowerFloor not only simplifies and accelerates their installation and assembly work, it also optimises sound protection. Due to sound decoupling on the feet (integrated) and on the frame sides (using the sound protection tape supplied), the ACO ShowerFloor system fulfils the requirements of both DIN 4109 and the stricter VDI 4100:2012 “Sound protection for residential buildings” in sound protection level III (LAF <= 24 dB(A)).

4. Conclusion

Sanitary installations are executed within the framework of a comprehensive set of rules and regulations. They demand not only technical know-how and craftsmanship skills, but also extensive theoretical knowledge. This applies in particular to the professional installation of shower channels. It’s not enough to have a good technical design and a high performance product.  It is also essential that the relevant rules and regulations are understood and seen as instructions to ensure a professional installation and not, as often happens, as an inconvenience.    


Dörte Mallohn

Product Manager Sanitary Drainage at ACO Building Drainage