What actually works
From the least risky to the most effective:
- Bell plunger, ten firm strokes, water covering the cup.
- Manual snake of 3 to 5 m, turning rather than pushing.
- Hot (never boiling) water plus dish soap for a greasy sink blockage.
- Baking soda and vinegar: fine as maintenance, not enough on a real blockage.
What not to do
Caustic soda attacks seals, weakens old PVC and becomes dangerous if a professional later has to open a trap full of product. In the stoneware stacks of Brussels houses it accelerates hemp joint decay.
Do not use a domestic pressure washer in a pan either: the pressure rebounds and can crack the ceramic.
When the problem is no longer yours
If water rises in several fixtures at once (toilet plus shower, or sink plus cellar), the blockage is on the shared stack or collector. In a condominium that is common property and the manager's responsibility.
Waste water backing up in a cellar after a storm can also come from a saturated public sewer: the real fix is a non-return valve, not unblocking.
Unblocking prices in Brussels
Ranges observed in 2026, call-out included, daytime.
- Manual or electric snake: €120–220 incl. VAT
- High-pressure jetting of a stack: €250–450 incl. VAT
- CCTV drain inspection: €150–300 incl. VAT
- Full collector cleaning in a building: on quotation