Stack pipe blocked? What to do in a flat or apartment

What is a stack?

The stack is the vertical waste pipe that runs through all floors of a building. The toilet, shower, washbasin and kitchen of each dwelling are connected to it. At the bottom the pipe connects to the sewer; at the top it runs through to above the roof, so the pipe can vent. Often there is also a separate pipe for rainwater. A single-family home also has a stack, but in a block of flats several households share the same pipe.

Signs of a blocked soil stack

• Water is coming up in your shower, bath, kitchen sink or toilet whilst you are doing nothing yourself. The water from the upstairs neighbours is looking for an outlet at the lowest point, and that is often a dwelling on the ground floor or a low floor.
• Several drains in your home are running away slowly at the same time.
• Your drain gurgles when the neighbours use water (see drain or toilet gurgling).
• There's a sewer smell in the property, the hallway or near the service shaft.
• Neighbours have the same complaints.

What causes a stack pipe to become blocked?

A soil stack collects wastewater from many households. Common causes are grease from kitchens, wet wipes, sanitary towels, kitchen roll and cat litter, and building debris after renovation. Often it blocks at the bottom, in the bend where the vertical pipe transitions into the horizontal pipe to the sewer.

What do you do immediately?

1. Stop using water, including the washing machine and dishwasher.
2. Warn the neighbours, especially the residents above you. As long as they use water, it will keep coming up into your property.
3. Limit the damage. Scoop water out of the shower tray, put down towels, place items higher and close the toilet lid.
4. Report it immediately to the owners' association (VvE) manager or the landlord. Outside office hours, many managers and landlords have an emergency number.
5. Take photos of the water and any damage, for the insurance and the managing agent.
6. Do not attempt to use a drain snake or high pressure yourself in the shared pipe. The blockage is usually outside your home, and with inexpert work you can damage the pipe or cause water to come up in other residents' homes.

How is a stack pipe unblocked?

A soil stack usually has rodding points: closable openings in the pipe, for example at the bottom in the cellar, the crawl space, the storage rooms or in the pipe shaft. Through such an opening, the pipe is cleared using a drain snake or high-pressure jetting. If the blockage keeps returning, a camera inspection will show whether there is subsidence, a fracture or stubborn deposits in the pipe.

Who is responsible?

A soil stack is usually a shared pipe. In an owner-occupied apartment it usually falls under the owners' association (VvE), in a rented flat under the landlord. The drain within your own home, up to the connection to the soil stack, is usually the responsibility of the resident or owner. Read more in sewer blocked: who pays?

Prevention

• Do not flush wet wipes, sanitary towels, kitchen paper or cat litter down the toilet, even if the packaging says "flushable".
• Let frying and cooking fat solidify and dispose of it with the residual waste.
• After renovation, do not dispose of building waste or tile adhesive residue via the drain.
• Share these tips with other residents, for example via the owners' association (VvE).

For The Hague and Delft: see also drain unblocking The Hague city centre and drain unblocking Delft.