What is happening
A drain that clears and comes back within weeks was never really fixed. Something is still in the line.
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:
- Grease and soap film rebuilding on the pipe wall
- Hard water scale narrowing an older cast iron line
- Roots at a joint, which regrow on a seasonal rhythm
- A belly holding water and catching whatever passes through
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
Timing is the useful clue. A line that fails at roughly the same time each year is usually roots, because root growth follows the season. One that gets steadily worse regardless of season is usually build-up on the wall. One that fails at unpredictable intervals often has a low section catching whatever happens to pass.
What guessing costs
The expensive version of guessing here is paying for four clearings a year indefinitely. At roughly the third repeat, the cost of finding the cause is less than the cost of continuing to treat the symptom.
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, hydro jetting is the service that most often resolves it, though we would confirm that by looking rather than by assuming.
