Plastic hose is safe for drinking water

Safely separate extinguishing and drinking water

So that health and hygiene can be maintained in the drinking water installation, the new DIN 1988-600 created a clear separation between drinking water installations and extinguishing water systems according to DIN 14462. The interface between the drinking water installation and the fire extinguishing and fire protection systems was determined by the extinguishing water transfer point (LWÜ). Thus, in DIN 1988-600, only the requirements are specified that must be complied with up to the extinguishing water transfer point in the drinking water installation. The requirements for fire extinguishing and fire protection systems are described in DIN 14462. Both standards are necessary for the planning and implementation of fire extinguishing and fire protection systems. The DIN / Beuth and ZVSHK commentary on DIN 1988-600 serve as the basis for this specialist article. The content of the ZVSHK membership edition and the DIN / Beuth edition are identical (Image 1).

Historically, there was a close connection between the public drinking water supply and the extinguishing water supply. Fire extinguishing and fire protection systems were integrated into drinking water installations as a matter of course. The amount of extinguishing water to be kept available and the resulting nominal widths of the pipe systems were not in a reasonable relationship to the actually required amounts of drinking water and flow velocities. The resulting risks for drinking water hygiene are now strictly separated from each other with the two new regulations DIN 1988-600 and DIN 14462.

The present part of DIN 1988-600 sets clear accents to ensure a hygienically perfect drinking water supply. Consequently, it is not only a question of maintaining hygiene in the drinking water pipe networks, but also in the house connection line and in the distribution lines in the building. The requirement is to dimension the pipe systems for drinking water requirements in the future. This results in restrictions in securing the extinguishing water supply, whereby it is consciously accepted that the water quantities necessary for fire protection have to be stored in case of doubt.

Whether it is possible to obtain extinguishing water from the public drinking water network for new systems or for the renovation of old systems must be clarified jointly between the operator, planner and water supply company. Ultimately, however, only the water supply company decides whether the amount of extinguishing water is made available for property protection. The water company also determines the contractual conditions.

Fire protection concept

According to the building regulations of the federal states, fire protection requirements are placed on the buildings for certain building classes (e.g. special structures). For building classes with fire protection requirements, fire protection concepts are part of the building permits. In the fire protection concepts, the fire protection goals for the entire building are described and are at the same time the basis for building and usage permits (Picture 2).

Systems according to DIN 1988-600 can be used for both preventive and defensive fire protection. When using extinguishing systems supplied with drinking water, it is important to plan and assess the effectiveness of the hygiene protection and the extinguishing effect. Preventive fire protection is the generic term for all measures that are intended to prevent or limit the occurrence, spread and effects of fires in advance and to enable the fire brigade to carry out the extinguishing work. Defensive fire protection is a task of the fire brigade. Together with the fire brigade's preventive fire protection, it enables the fire to be extinguished, contained or prevented from spreading.

Extinguishing water transfer point (LWÜ)

The drinking water installation ends with the extinguishing water transfer point and the fire extinguishing and fire protection system begins. With the LWÜ, the protection of the drinking water is ensured and repercussions from the fire extinguishing and fire protection system on the drinking water installation are excluded. The drinking water connection must be set up by a contract installation company in accordance with AVBWasserV. The approval of the water supply company is required for direct and indirect connection of a fire extinguishing and fire protection system to the drinking water installation (Picture 3).

Direct connection station (DAS)

The direct connection station is only permitted for connecting a sprinkler system or extinguishing system with open nozzles to the drinking water installation. When using the valve, it must be ensured that the drinking water requirement is greater than the extinguishing water requirement. The extinguishing system is separated from the drinking water installation by means of an atmospheric area that is drained in the standby state. If the extinguishing system is triggered, the connection is established automatically and the flow rate is displayed. According to DIN 14464, DAS with system separation or double shut-off are possible.

Connecting cable

In the sense of DIN 1988-600, the connection line is the connection between the supply line of the public water supply and the main shut-off device, i.e. the first valve in the building or water meter shaft (Picture 4). The planning and execution of the connection line is carried out on the basis of the relevant DVGW regulations (e.g. leaflet W 404) by the water supply company. When dimensioning the house connection as well as the commitment to deliver extinguishing water for property protection, the supply company must ensure that the minimum supply pressure in the supply network is not fallen below. A secure supply of drinking water to the population must therefore also be ensured during the extraction of extinguishing water for property protection.

The planner must provide the supplier with the necessary information for dimensioning the connection line, taking into account the fire protection concept. The drinking water requirement must be determined and it must be checked whether the extinguishing water requirement can also be covered. By pointing out that drinking and fire-fighting water for a property must be supplied via a common connection pipe, hygiene is guaranteed in the connection pipe. If the water supply company only provides partial quantities of the required extinguishing water, the missing quantities must be stocked up. The storage amount also depends on the duration of the extinguishing process and the type of system and must be calculated.

The quantities of extinguishing water for property protection are usually recorded in the same way as the drinking water requirement using a calibrated water meter. The selection of the water meter as well as the technical framework conditions of the water meter system are specified by the water supply company. It must be ensured here that the drinking water consumption must be recorded with sufficient accuracy in accordance with the legal calibration requirements. However, the water meter must also be able to measure the volume flow when the fire extinguishing and fire protection system is in operation. Compound metering systems are usually used.

Individual feed lines to extinguishing water transfer points

The line that branches off directly from e.g. a distributor and leads to an LWÜ according to DIN 1988-600 is referred to as a single feed line to a transfer point. As a rule, this part of the line is not or only rarely operated. This leads to stagnation with its negative consequences for drinking water. For this reason, the volume here is limited. On the one hand, the length of the pipeline must not be more than 10 x DN. It is important to ensure that it is the geometric length filled with drinking water. On the other hand, the line volume must not exceed 1.5 liters. In general, the protection goal of avoiding stagnation applies.

In practice, these specifications can only rarely be complied with due to the specified installation conditions and cable routing, especially in larger systems. For this reason, flushing devices are to be provided which automatically ensure a sufficient exchange of water. Since the valve is used in drinking water, slowly closing fittings approved for drinking water must be used, which do not generate any pressure surges during the opening and closing process. At least three times the water volume of the entire individual supply line must be exchanged in order to meet the hygienic requirements.

In addition to the volume of water to be exchanged, the flow velocity occurring in the pipeline during the flushing process plays an important role. It is specified here that this must be at least 0.2 m / s during flushing for lines up to and including DN 50 in relation to the pipeline to the LWÜ. For lines larger than DN 50, a flushing flow rate of 0.1 m / s must be achieved. The background to these specifications is to ensure turbulent flow conditions in the pipeline (Pic 5).

Materials for pipe systems

Drinking water pipes (pipes and connectors) and fittings up to the extinguishing water transfer point as well as the subsequent pipes to fire extinguishing and fire protection systems must consist of non-combustible materials or metallic materials if they are freely laid inside buildings. These pipe materials are listed in Table 2 of the standard. Lines laid underground can also be installed from plastic materials. Plastic pipes can be installed within house connection rooms - within the meaning of this standard, these are also technical rooms in which the house connection line is introduced - if the structural fire protection requirements and the guidelines on fire protection requirements for line systems (LAR line system guideline) of the respective federal state are complied with. As a rule, the components and the penetrations in such house connection rooms of building classes 4 and 5 as well as the special structures are to be fire-resistant with requirements F90, so that fire protection can be observed can. If plastic connecting cables are introduced into rooms that do not meet fire protection requirements, the transition to metal systems must be made immediately after the point of introduction. The plastic components in front of it must be protected against fire.

Distribution pipes and risers made of plastic

If distribution and riser pipes from the drinking water pipe leading to a fire extinguishing and fire protection system are made of plastic or multi-layer composite pipe materials - flammable materials - a non-flammable metallic pipe material according to Table 2 of the standard must be used up to the valves that close automatically in the event of the extinguishing water being withdrawn (Pic 6). The automatically closing valve - generally called drinking water sealing - must be designed in such a way that it closes automatically in the event of a fire. If valves are used for this which require external energy for operation, for example motor-driven shut-off devices, they must be designed in such a way that they are closed without current.

Plastic drinking water pipes to TYPE S fire hydrants

The connection of self-help facilities type S with plastic or multilayer composite pipes is permitted if they are concealed with a covering of at least 15 mm or behind non-combustible surfaces made of mineral building materials with a minimum thickness of 15 mm in the usage units (e.g. bathrooms, toilet facilities or other wet rooms). This means that the wall hydrants type S in concealed drinking water installations made of plastics that comply with the above. Meet requirements, can be integrated (Pic 7).

In the case of drinking water installations with a type S wall hydrant, the distribution and riser pipes must be made of metallic materials if another fire extinguishing and fire protection system is connected to the drinking water installation. Automatically closing fittings at the connection of the storey or individual connection line are not required in these cases (Picture 8).

Shut-off valves

Shut-off valves must be secured against unauthorized closing, e.g. by means of valve shut-off devices. If the shut-off valves are installed in rooms that are only accessible by authorized personnel, such as regularly locked house connection rooms, this usually already provides sufficient protection against unauthorized operation. An additional safeguarding of the individual fittings can thus be omitted, but the fittings still have to be labeled (Pic 9). Drinking water pipes up to the extinguishing water transfer point are to be marked in accordance with DIN 2403 (Pic 10). If a drinking water line branches off from the supply line to a fire extinguishing and fire protection system, it must be able to be shut off separately.

Filling and emptying station

Filling and emptying stations (FE station) according to DIN 14463-1 with DVGW certification mark are extinguishing water transfer stations (LWÜ) that can be connected directly to the drinking water network. The pipe system behind an FE station is a wet / dry extinguishing water pipe. The pipe system for wall hydrants (self-help / fire brigade use) behind the station must be flooded after 60 seconds at the latest in accordance with DIN 14462. In wall hydrant systems, the water supply is closed again after all hose connection valves in the wall hydrant have been closed. The FE station emptying then opens and the pipe system is emptied automatically. The FE station then switches back to standby mode. The extinguishing water pipe after the FE station must be installed with a slope of 0.5% to the station in order to drain the residual water via the FE station after the system has been reset. If there is extinguishing water in pipe sections that cannot be emptied via the FE station, additional automatic emptying (hydraulic or electric) must be provided (Pic 11).

Since when the system is triggered, the water flows wet / dry into the extinguishing water pipe, the existing air is pushed in the direction of flow. The air must escape from the pipeline network as quickly and evenly as possible through ventilation valves in accordance with DIN 14463-3, in order to fill the extinguishing water pipeline with water as quickly as possible and, if necessary, to avoid pipeline damage (Pic 12).

Drinking water installation with wall hydrant type S

The direct, immediate connection of wall hydrants is generally only permitted for type S wall hydrants in accordance with DIN 14461-1. These wall hydrants are characterized by the fact that the extinguishing water output of the individual wall hydrants is designed for 24 l / min and the wall hydrant is therefore equipped with a hose connection valve DN 25 and a dimensionally stable hose with a nominal width of DN 20 on the reel. The hose connection valve must be equipped with a backflow preventer and aerator as a safety combination (Pic 13). Under no circumstances may the wall hydrant itself be the last connection in the pipe system if this branch line is longer than 10 x DN or contains a water volume of more than 1.5 l.

Wall hydrants with greater water capacities, such as type F with a wall hydrant valve DN 50 and a dimensionally stable hose with a nominal diameter of DN 25, as they were installed almost without exception until 2002, or wall hydrants with fire service pressure hose C-42 / C-52, on the other hand, must not be connected directly the drinking water network must be connected. The supply line to the individual wall hydrants is to be treated like a drinking water pipe and must therefore be dimensioned exclusively taking into account the drinking water peak volume flow according to the specifications in DIN 1988 and DIN EN 806. Sufficient flushing of the lines must always be ensured.

External feeds

The set of rules ties in seamlessly with the set of rules of DIN EN 1717 and DIN 1988-100, according to which the supply and connection of drinking water with non-drinking water networks must only take place via the free outlet type AA or type AB (Fig. 14).

Treatment of existing systems

In particular, insufficiently flowing drinking water pipes in the area of ​​fire extinguishing and fire protection systems can be the cause of an acute health hazard, which can result in the renovation of existing extinguishing systems as a technical remedial measure. If the limit values ​​of the Drinking Water Ordinance for drinking water in these stagnant or non-flowing pipes are not complied with, the drinking water installation connected to this system will not be protected.

If remedial measures have to be initiated due to inadequate hygiene, the requirements of DIN 1988-600 must be implemented. As a rule, the requirements for fire protection must then also be checked and adjusted. If the fire protection concept has to be changed or adapted, all parties concerned must be involved so that, in addition to the drinking water hygiene requirements, fire protection issues are also adequately taken into account.

The fire protection assessment of a renovation or a conversion measure does not necessarily have to mean that all extinguishing systems have to be brought up to date with the latest technology.This is where the competent authority, as the highest competent fire protection authority, is usually in conjunction with the fire brigade, when reviewing conversion, renovation and repair measures or changes in use, whether a new fire protection concept needs to be drawn up or whether there is existing protection because there are no fundamental changes in the legal Requirements have emerged.

Installation

According to VOB DIN 18381, the contractor must carry out a functional test before the systems (in this case the drinking water installation) are put into operation. The technical regulation for the implementation of commissioning for drinking water installations is DIN EN 806-5 "Operation and maintenance", in this case up to the extinguishing water transfer point (LWÜ). For the fire extinguishing and fire protection systems beginning with the LWÜ, the specifications of the standards DIN EN 12845, DIN 14462, DIN EN 671-3, DIN 14494 and DIN 14495 must be observed for operation and maintenance. With regard to the wall hydrant systems, the commissioning tests, which can be carried out by a fire protection specialist, are regulated in DIN 14462. In particular, the proper functioning of the fire protection equipment is checked.

A distinction must be made between this commissioning test and the acceptance test, as it is also to be carried out in many federal states by a recognized fire protection expert, e.g. B. in NRW according to the PrüfVO NRW. If such ordinances exist in the respective federal state or such an acceptance test is required by building regulations, this may have to be carried out additionally. For this purpose, the responsibility for the implementation and the assumption of costs should be contractually agreed with the client in advance. In principle, the operator is responsible for carrying out the acceptance test according to the status of the ordinance, but in practice this task is often shifted to the installation company.

For reasons of liability law, commissioning and, if applicable, the acceptance test carried out must be recorded and the evidence handed over to the customer when his technical system is handed over. A control book according to DIN 14462 must be created for fire extinguishing and fire protection systems (Pic 15).

maintenance

Compliance with and implementation of the fire protection protection goals is not only binding for all those involved in the construction, such as architects, specialist planners and executing companies, but also obliges the building owner or operator to always keep the fire protection systems in a functional condition. Because fire protection systems are not subject to fitness training, as there is no regular triggering or actuation, systematic checks by experts are necessary. Because even after years or decades, in the event of a fire - which ideally never happens - the fire protection equipment must function reliably and be operational.

In the specific regulations, such as DIN 14462, the activities for reviews, inspections and maintenance, which are to be carried out at regular intervals, are specified. The operator must be aware of this so that he can meet his obligations for the safe operation and use of the building.

Conclusion

Due to the strict separation of drinking water installations that end at the extinguishing water transfer point according to DIN 1988-600 and the fire extinguishing and fire protection systems that start after the extinguishing water transfer point according to DIN 14462, the user will need both sets of rules for qualified planning and execution in the future.

The next issue of the SBZ will deal with the subject of DIN 14462 "Extinguishing water facilities, planning, construction and operation".