In apartment buildings, there is a recurring odor problem that almost always has the same cause: fat deposits in the riser pipes. What comes out of the kitchens on lower floors accumulates in the vertical main pipes on its way down and begins to rot there. The result is diffuse odors in the apartments, especially on the lower floors – even when individual drains are completely clean.
Why the riser pipe is the problem
A typical apartment building has two central vertical sewage systems: the wastewater and the rainwater pipes. In the wastewater system, all kitchen drains from all apartments flow into the same riser pipe. Over the years, fat layers several centimeters thick build up there, especially in the connection areas of the individual floors.
Diese Fettschichten haben zwei direkte Folgen: Sie reduzieren den Innendurchmesser der Leitung und führen zu langsamerem Abfluss aus den Wohnungen. Und sie bilden den Lebensraum für anaerobe Fäulnisbakterien, die Schwefelwasserstoff (das berühmte „faule Eier“-Aroma) und andere geruchsintensive Stoffe produzieren.
What classic solutions achieve – and what they don't
High-pressure cleaning by specialist companies
Works mechanically – removes part of the fat deposits. Typically costs €800 to €2,500 per riser pipe and must be repeated every 12 to 24 months in apartment buildings because the cause (continuous fat introduction from the kitchens) is not addressed.
Chemical flushing
Occasionally offered by plumbers. Only moves the fat further down into the piping system or into the sewage treatment plant, where it causes problems. Furthermore, it is often not DWA-compliant and can be damaging to the material of the riser pipe itself.
Emergency services
When a blockage becomes acute, emergency services are called. This costs €200 to €600 per call and occurs 2 to 6 times per year in neglected buildings.
The biological way: monthly dosage
An effective and predictable alternative is the monthly application of a biological cleaner such as lipasanF® directly into the riser pipe. 1 to 5 liters per residential unit are recommended, depending on the number of connected units and the duration of the buildup.
The property management guide describes the exact procedure. In practice, the agent is usually introduced via the uppermost connection into the riser pipe or directly into the grease trap in the basement. The lipase microorganisms migrate down along the pipe wall and begin to enzymatically break down the fat layers into fatty acids and glycerin.
What you can expect after 3, 6, and 12 months
After 4 to 8 weeks: Spürbare Reduktion der Geruchsbeschwerden aus den Wohnungen. Mieter melden, dass „der Geruch aus dem Abfluss“ verschwindet – auch wenn ihre eigenen Siphone sauber waren.
After 3 to 6 months: Measurable improvement in drainage speed in the apartments. The improvement is not spectacular, but perceptible, especially on the top and bottom floors.
After 9 to 12 months: Emergency calls have significantly decreased, often to zero. Annual cleaning costs have practically been reduced by the emergency service portion.
Cost calculation in this example
For a typical building with 12 residential units:
- Previous emergency service costs: €800 to €2,400 per year
- Possible high-pressure flush every 18 months: €1,200 → allocated €800/year
- Cost of lipasanF® application monthly (5 L per month): approx. €900/year
The pure material usage is therefore comparable to emergency service costs. The decisive advantage is the predictability – no more sudden €1,500 invoices, and no tenant complaints that create administrative effort.
Important notes
Tenants must be informed that no chemical drain cleaners should be used in the drains anymore – otherwise, the lipase microorganisms will be killed every time. A short notice in the stairwell is usually sufficient.
With very old house connections featuring lead pipes or severely damaged lines, biological treatment is no substitute for renovation. In these cases, however, it helps to extend the interval between renovations.