How to locate the likely blockage
Test fixtures one at a time. One slow basin or shower usually points to hair, grease or debris nearby. Several affected fixtures on the same side of the home suggest a branch pipe; problems across floors may involve the stack.
Stop using water if flushing a toilet makes water rise in the bath or shower. The next large discharge could overflow indoors.
Safe checks you can make
Remove debris from the grate, inspect an accessible trap and use a plunger with the overflow sealed. Put a container below the trap and check every joint slowly after reassembly.
Never mix drain chemicals. Do not dismantle pipework containing a corrosive product, and tell the plumber exactly what was used.
Why a blockage returns
The cause may be poor fall, a sagging or narrowed pipe, grease deposits or a foreign object. A small temporary channel can close again quickly.
Mechanical cable cleaning reaches a longer section and removes denser deposits. Cable and cutter choice depends on pipe diameter, material and access.
When the call-out is urgent
Stop discharging water if waste backs up through a floor drain, the toilet level rises, a joint leaks or a neighbour could be flooded. A shared stack issue may affect several apartments.
Describe every affected fixture, any chemical used and access to the trap or clean-out. A photo or short video helps the plumber bring suitable equipment.
What affects the price
Cost depends on the location and length of the restriction, pipe diameter, access, whether a fixture must be removed and the cleaning method. The work is confirmed before it starts.
Frequently asked questions
Can I pour boiling water into plastic drains?
Boiling water can deform some plastic parts or seals. Use hot rather than boiling water only when the pipe material is known.
When will a plunger help?
It can clear a soft local restriction close to the outlet, but not usually a deep blockage, solid object or stack problem.
Why does the drain still smell?
Check that the trap contains water, joints are sealed and deposits have been removed from the pipe.
What should I tell the plumber?
List the affected fixtures, describe backing-up, gurgling and odour, disclose chemicals and send a photo of the access point.