What is happening
The floor drain sits lowest in the system, so it is usually the first place a main line problem shows itself.
Drains report problems indirectly. The fixture showing the symptom is often not where the trouble is, which is why the useful first question is not what is blocked but which fixtures are affected and when.
What usually causes it
In this area, four explanations cover most cases:
- A restriction in the main line
- Roots at a joint in the lateral
- A collapsed or offset section
- Storm water finding its way into the sanitary line
Which one applies changes the fix entirely, and they are not distinguishable from inside the house. We would want to see it before saying anything for certain.
What you can check yourself
Run the fixtures one at a time and note which ones react to each other. Two drains that respond to one another share a pipe, and that narrows things considerably.
Note whether it is getting worse gradually or started suddenly. Gradual usually means the pipe has been closing up for a long time. Sudden usually means something specific is in the way.
Narrowing it down
Check whether it happens only when other fixtures are used, or on its own. Reacting to the washing machine or a shower points at the shared main. Backing up with no other water running suggests something further out, or ground water entering the line.
What guessing costs
This is the one symptom on this list we would not suggest waiting on. A floor drain backing up means waste water is already choosing the lowest opening in the house, and the next place it goes is the floor.
When it is worth calling
If it has happened before, it is worth finding the cause rather than clearing it again. A drain that has been opened twice and returned twice will return a third time.
On this particular pattern, main line cleaning is the service that most often resolves it, though we would confirm that by looking rather than by assuming.
