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True Trade Path

Diagnostic guide

Drain Keeps Clogging

Tell the difference between a local fixture clog and a main line problem before you spend money on the wrong fix.

System
Plumbing
Causes covered
6
You can check
3 without a technician

Stop and read this first

  • Do not use chemical drain openers before a plumber visits. They splash back during mechanical clearing and cause chemical burns.
  • Sewage backup is a biohazard. Keep children and pets away and disinfect any affected surface thoroughly.
  • If sewage appears at multiple low fixtures at once, stop using all water in the house until the main line is cleared.

Work through these in order

Ordered from most to least likely. Working top down means you rule out the cheap, common causes before paying anyone to look at the expensive, rare ones.

  1. Hair and soap buildup in the trap

    CommonYou can check
    How to check
    Only one fixture is slow, and the rest of the house drains normally.
    The fix
    Remove and clean the P-trap, or use a drain snake. Avoid chemical drain openers — they damage pipe and make later professional work hazardous.

  2. Grease accumulation in a kitchen branch

    CommonYou can check
    How to check
    The kitchen sink is slow and worsens gradually. A garbage disposal is present.
    The fix
    Snake the branch line. Stop putting grease down the drain; it solidifies as it cools and coats the pipe wall.

  3. Blocked vent

    PossibleNeeds a pro
    How to check
    Drains gurgle, traps bubble, or water drains slowly with a glugging sound even when the line is clear.
    The fix
    A plumber clears the vent stack at the roof. A vent blocked by a nest or ice prevents air entering, so drains siphon rather than flow.

  4. Root intrusion in the sewer lateral

    CommonNeeds a pro
    How to check
    Multiple fixtures slow at the same time, and the lowest drains in the house back up first. Common in homes over forty years old with mature trees.
    The fix
    A plumber cameras and clears the lateral. Roots return, so recurring intrusion usually points to lining or replacement.

  5. Bellied or collapsed sewer line

    PossibleNeeds a pro
    How to check
    Clogs return within weeks of every cleaning, always in the same place.
    The fix
    A camera inspection identifies the defect. A belly holds water and solids and cannot be fixed by snaking.

  6. Flushed items in the line

    CommonYou can check
    How to check
    A single toilet backs up and plunging does not clear it. Common with wipes marketed as flushable.
    The fix
    A closet auger usually retrieves the obstruction. Persistent blockage means the toilet must be pulled.

Once you know what it is

Step one

Know what it should cost

Get the range before you call, so the first number you hear is not the only number you have.

Step two

Decide repair or replace

On equipment near end of life, the repair is usually the first of several.

Step three

Check the quote

Compare against the typical range and confirm the terms before you sign.

Estimate the repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms