Roots cause intermittent backups

Kitchen sink draining slowly while other fixtures run clear, with a plumber's inspection light on the counter

Quick Answer:

If kitchen drains back up sometimes while you’re rinsing or using other fixtures, roots in the lateral sewer line are a likely cause. Time and record each event, try a few quick plumbing checks you can do safely, and if backups return arrange a camera inspection with your plumber so the intermittent intrusion can be captured.

Why This Happens

Tree and shrub roots naturally seek water and small cracks in older pipes. When roots reach a lateral they can intrude only at certain levels of flow or pressure. That creates backups that come and go depending on which fixtures are running, how full the pipe is, and where the roots flex into the line. Small, shifting root beds can cause a backup caused by roots pattern that is intermittent rather than constant.

Step-by-Step What to Do

1. Time and record each backup event

  • Keep a simple log for a few days during kitchen cleanup times. Note the exact time, which fixtures were in use (kitchen sink, dishwasher, garbage disposal, laundry, toilet), and how long the backup lasted.
  • Even small details help: whether you used hot water, ran the disposal, or flushed a toilet.

2. Try successive sink plunges

  • Use a sink plunger on the affected fixture. Perform several firm plunges rather than a single long attempt. This can dislodge minor blockages near the fixture.
  • If plunging improves things temporarily, that suggests the restriction is not too far down, but it doesn’t rule out root intrusion deeper in the lateral.

3. Remove and inspect the P-trap

  • Place a bucket under the trap, loosen the slip nuts, and remove the P-trap. Check inside for roots, stringy material, or solids caught near the trap area.
  • If you see root fibers in or just beyond the trap, that confirms root entry close to the fixture side of the line. If the trap is clean but backups continue, the problem is likely deeper.

4. If traps are clear, arrange a camera inspection

  • Because the issue is intermittent, ask the plumber for a camera inspection that can be scheduled when you’re likely to reproduce the backup. A live or recorded camera run can capture roots flexing into the pipe during specific flows.
  • Give the plumber your event log and timing so they can reproduce the condition—running the dishwasher, disposing of food, or simultaneous fixture use may be necessary to make the intrusion appear on camera.

What Not to Do

  • Don’t assume intermittent backups are just grease. Roots can mimic grease-like blockages by allowing partial flow until pressure changes.
  • Avoid repeatedly using chemical degreasers. They can damage pipe materials, harm septic systems, and dissolve organic matter in ways that obscure root material on camera.
  • Don’t wait until the backups become constant. If the events are unpredictable or increasing in frequency, call a professional before the line fails entirely.

When to Call a Professional

Call a plumber when backups are unpredictable, getting worse, or if you found root material in the trap. If your plumber confirms roots are entering the lateral, you’ll need a camera inspection and a professional plan for cutting and treating or repairing the pipe. If the house or property was recently landscaped or altered, mention any work—post-construction shifts can encourage root growth near the line, similar to issues described in roots after a remodel.

Safety Notes

  • Wear gloves and eye protection when removing a P-trap. Waste water can contain bacteria and contaminants.
  • Have a bucket and rags ready and clean up spills promptly. Sanitize tools and hands after the inspection.
  • If you’re uncomfortable with any step, stop and call a licensed plumber. Avoid DIY repairs that require cutting the line or working in confined spaces.

Common Homeowner Questions

  • Why do roots only block sometimes? Roots may flex into a crack under certain flows or pressures and retract at other times, causing intermittent flow restriction.
  • Will snaking fix this? Snaking can remove some root material but often does not stop regrowth; camera inspection and proper repair are usually needed.
  • Can I prevent this myself? Routine checks and avoiding planting near sewer lines help, but established root intrusion usually requires professional repair or treatment.

More in this topic

For more related fixes and similar symptoms, see Tree Root Intrusion Patterns.

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