Leading in drainage
Führend in Entwässerung
KESSEL Logo
search:
 
 >  > Austrian standard ÖNORM B 2501 revised

Product search:


Please enter an article number or search word to find technical data, specification text and CAD drawings of the product in question.

Austrian standard ÖNORM B 2501 revised

Due to the rising costs of building lots and construction, it is becoming more and more common that basements of buildings are being designed or converted into living areas such as apartments, offices or children’s rooms. It is exactly these low lying areas that are at high risk of backwater damage. In these cases the building planner or engineer as well as the plumbing installation companies have the responsibility offering the proper solution for each individual case.

On April 1, 2015 the revised ÖNORM B 2501 ‘Drainage Systems for Buildings and Property Lots’ was released which replaces the previous norm from 2009. In addition the ÖNORM EN 12056 must be considered which is the ‘basis norm’ and sets the basic regulatory guidelines. Within these basic regulatory guidelines, national guidelines are also allowed. These national requirements have been defined in the ÖNORM B 2501 and with the revision have been brought up to current technical standards.

This presents a challenge for the planners and installation companies in that they understand the requirements of ÖNORM EN 12056 as well as the requirements of ÖNORM B 2501. As the leading manufacturer of backwater protection systems, KESSEL has created this guide to help simplify and clarify the planning and installation of backwater protection systems related to ÖNORM B 2501 Section 5.6.

Section 5.6 Backwater protection of domestic wastewater

5.6.1 Revision of ÖNORM EN 12056-1:2000 Section 5.5.1

The locally backwater level is defined as being 15 cm over the level of the nearest sewer manhole cover or inlet (as seen in the opposite direction of natural drainage flow) connected to the home or building. If the locally defined backwater level is not easily determined, the local topography (hills, depressions) as well as street levels, underpasses and flood prone areas must be used to determine the local backwater level. 

A significant step in the planning of drainage systems and backwater protection is the determination of the physical effective backwater level as a reference point. Required to determine this is:

  • The standing water level in a water trap for wastewater drains
  • The top level of rainwater / surface water drains (top of cover)
  • The highest effective reference point from the connected sewage piping

The additional 15 cm of height over the sewer manhole cover offers additional safety in the event of backwater. All open drainage fixtures under the defined backwater level must be protected from backwater.

Revision to ÖNORM EN 12056-5:2000 Section 10

The user’s manual of the drainage system must state that drainage fixtures or systems which are not in use must have a manual closure system which is in the closed position.

The requirement until now was that backwater valves must always be in the closed position. This requirement has been reduced in the revised norm to ‘systems which not in use’ which better relates to what happens in the field. Now, the backwater valve needs to be locked closed only during times of non-use – for example during vacation when the house is not occupied.

Section 5.6.2.2.1  Drainage with natural slope to the public sewer.

When the drainage fixture is below the locally defined backwater level, the wastewater is to be pumped into the public sewer with a lifting station (with backwater loop) according to ÖNORM EN 12056-4:2000, Picture 2 or with a backwater lifting station.

The norm applies two different applications to determine the proper system to choose for backwater protection. If a natural slope between drainage fixture and public sewer is available, a wastewater lifting station or backwater lifting station should be used. Alternatively, a backwater valve can be used in specific circumstances.

An effective basement drainage system is based on the local conditions and should follow the rule ‘gravity drainage has priority’. This means, wastewater should drain with gravity whenever possible – this saves money and energy. As soon as the drainage fixture is below the public sewer level (or does not have sufficient slope to the sewer according to 5.6.2.2.2), a wastewater lifting station must be used – this is significantly more expensive as a backwater valve. Not only the purchase price of a lifting station is significantly higher but also the daily operational costs as well as service and maintenance fees. Every liter of wastewater draining from a shower, WC or washing machine into the lifting station must be pumped – this requires energy.

Section 5.6.3   Backwater protection with domestic wastewater and rainwater for renovation of existing buildings

e) In the case that rainwater is collected below the locally defined backwater level (and cannot simply drain / leach into the earth) it must be pumped into the local sewer with a lifting station or a backwater valve lifting station. In the case that the rainwater collection area is less than 10 square meters (and meets other requirements) and has a natural slope to the public sewer, then this area may be protected by a backwater valve according to ÖNORM EN 13564-1

Rainwater collected below the backwater level can only be drained into the public sewer via an automatic operating lifting station or backwater lifting station.

Section 5.6.3  Backwater protection with domestic wastewater and rainwater for renovation of existing buildings.

h) In the case that all floors of a building (including the basement) is drained through a single wastewater pipe, backwater valves in combination with an upstream wastewater lifting station may be used.

The use of a single wastewater pipe for an existing building is only allowed if other measures, such pipe modifications, proves to be non economical.  This single pipe transfers all wastewater from the home through a single pipe (regardless if the pipe is above or below the backwater level) directly into the public sewer. For these special cases, ÖNORM B 2501 Backwater Lifting Stations takes effect. These hybrid solutions combine the safety of a lifting station with the efficiency of gravity drainage. A hybrid system normally operates without power, without interruption and with minimal wear and tear on the pump.

Section 5.6.2.2.1  Drainage with natural slope to the public sewer.

A lifting station or backwater lifting station is not required in the following cases:

1) the rooms below the backwater level are considered to be not important meaning if these rooms flood with backwater, considerable damage to property is not expected and the health of people is also no put at risk.

2) the amount of people effective by backwater at this site is small and there is another WC located above backwater level that can be used in case the drainage fixtures below backwater level are off line.

3) in the above cases backwater valves Type 2, 3 and 5 are allowed when connected to wastewater pipes without a WC connected to them. If a WC is connected to the wastewater drainage pipe then a Type 3 backwater valve is required according to ÖNORM EN 13564-1.

In the previous version of ÖNORM B 2501, Type 2 backwater valve (with free hanging, vertical backwater flaps) were allowed for wastewater containing raw sewage (WC connection). However, field experience has shown that the free hanging flaps slow the flow of wastewater which can lead to blockages of the wastewater pipe and malfunctions.

The ÖNORM revision now requires that Type 3 backwater valves are installed in wastewater pipes containing raw sewage (WC connection). A type 3 valve is a powered backwater valve with automated closure device which during normal operation is in the open position and closes only in the event of backwater.

Section 5.6.3   Backwater protection with domestic wastewater and rainwater for renovation of existing buildings

e) In the case that rainwater is collected below the locally defined backwater level (and cannot simply drain / leach into the earth) it must be pumped into the local sewer with a lifting station or a backwater valve lifting station. In the case that the rainwater collection area is less than 10 square meters (and meets other requirements) and has a natural slope to the public sewer, then this area may be protected by a backwater valve according to ÖNORM EN 13564-1

Rainwater collected below the backwater level can only be drained into the public sewer via an automatic operating lifting station or backwater lifting station.

Section 5.6.3  Backwater protection with domestic wastewater and rainwater for renovation of existing buildings.

h) In the case that all floors of a building (including the basement) is drained through a single wastewater pipe, backwater valves in combination with an upstream wastewater lifting station may be used.

The use of a single wastewater pipe for an existing building is only allowed if other measures, such pipe modifications, proves to be non economical.  This single pipe transfers all wastewater from the home through a single pipe (regardless if the pipe is above or below the backwater level) directly into the public sewer. For these special cases, ÖNORM B 2501 Backwater Lifting Stations takes effect. These hybrid solutions combine the safety of a lifting station with the efficiency of gravity drainage. A hybrid system normally operates without power, without interruption and with minimal wear and tear on the pump.

 

Imprint / Impressum | Privacy policy
©2013 KESSEL AG, Bahnhofstraße 31, 85101 Lenting, Germany