Protecting your cellar from flooding

After rainstorms, homeowners often have to deal with flooded cellars or other rooms at or below ground level. This is usually caused by a lack of sewer backflow protection measures in cellars or faults in existing systems. Only a fully functioning house sewer can protect a cellar from flooding. Real estate and home owners are responsible for their own house sewers.

Things to check

• Are all sewer lines that lead from the house to the public sewer leak free?
• Are all floor drains, shower trays, sinks and washing machines in the cellar or on other floors below street level secured against backflow?
• Are all toilet drains below street level secured against backflow with a faecal lifting plant?
• Access covers (on access pipes for cleaning) must be closed properly to be watertight. Commercially available access covers can withstand higher than normal water pressure.
• Double flap backwater valves must be kept closed manually and opened before using the drainage sources. They should be closed again after use. They may only be installed in secondary sewer lines, not in the main sewer lines. Single flap backwater valves do not provide complete security.
• Generally, a lifting plant is the best security measure for any drain points situated below backflow level.

Sewer backup

Causes

A sewer backup can be caused by high water flows due to rainstorms.

Backflow level

The backflow level is the highest water level to which wastewater can rise in a sewer system. On level streets, it is usually at the pavement level at the nearest manhole (or ten cm above street level).

How it works

During heavy rain, the water level in the sewer can rise up to the backflow level. This water flows into the pipes of the house sewer system. Any drains that are below backflow level are at risk of backflow, because the water that exceeds the available space in the sewer seeks an outlet with enormous pressure and can flow out of any openings that are not secured against backflow.

Where can backflow occur?

• Unsecured toilet in the cellar
• Unsecured sink in the cellar
• Unsecured floor drain in the cellar
• Leaking/not fully closed access cover in the cellar

Kontakt

• Wien Kanal
• 1030 Vienna, Modecenterstraße 14/Block C
• Phone: +43 1 4000-8030, Monday to Friday 7.30 am bis 16.30 pm

Emergency hotline

If your toilet or house sewer is blocked or your house sewer has a fault, you can call our emergency hotline 24/7 all year round: +43 1 4000-9300

Download

Information leaflet: 2 MB PDF (German)

Further information

For more information, contact a plumber, architect or HVAC engineer.