When wastewater is backing up right now

Wastewater is coming up somewhere in the building right now.

This page is short on purpose. If wastewater is coming up in your building, the useful actions are few and the diagnosis can wait.

What this page cannot establish

noticing this establishes that you noticed it — it does not establish a cause
this page cannot establish what is obstructing or damaging the line
this page cannot establish whether the problem is on the private side or the public side
this page cannot establish whether the line requires repair or replacement
this page cannot establish whether the same thing will happen again

What a professional will be trying to work out

These are the distinctions a professional makes when they attend. They are questions, not conclusions — and knowing them lets you follow the conversation rather than just receive its result.

how many fixtures and which ones are affected
whether the affected fixtures share a run downstream
whether flow is still entering the system from anywhere in the building
whether the same thing has happened before, and how recently
whether anything about today differs from an ordinary day

What is worth writing down

These details are cheap to record now and impossible to reconstruct later.

the time it started and the time of each change
which fixtures were affected, in the order you noticed them
what water was running in the building beforehand
photographs of the affected area before cleanup, if you can take them safely

Evidence that would change the next decision

If you are deciding whether something is worth paying for, these are the things that actually move the decision.

which fixtures are affected and which are not
whether the lowest drains in the building are involved
whether it started during or after a period of heavy water use
whether the operating authority has other reports nearby

What would change the answer

which fixtures are affected and which are not
whether the lowest drains in the building are involved
whether it started during or after a period of heavy water use
whether the operating authority has other reports nearby

What to do next

The details you can capture during the event are the ones nobody can reconstruct afterwards, and they are what a professional asks for first.

Prepare what to tell the professional who attends

If your situation is different

This has happened before: Blockages that keep coming back
You suspect the wider public system is involved: The public sewer main
You do not know whether this is your responsibility: Who owns the lateral

Municipal call
Many operating authorities will check the public side when a backup is reported.
Public sewer main
Whether the wider system is involved changes who you should be calling.
Insurance and programs
Whether a policy responds to a backup is a question worth asking early, while the event is documented.