Drains & sewer
Why is my basement floor drain backing up?
Updated
Short answer
When water comes up through the basement floor drain, the main sewer line is usually blocked between the house and the street. Stop using water upstairs, then call a plumber to clear the main line. If it happens more than once, a camera inspection shows the cause.
Why the floor drain is first
The floor drain is the lowest opening in the plumbing. When the main is blocked, water from upstairs fixtures has nowhere to go but up, through the lowest drain. That's why a load of laundry or a shower can flood a basement.
Common causes on the Front Range
- Tree roots in clay or older sewer joints
- Grease buildup from kitchen drains
- Wipes and paper products
- A sag or offset joint caused by soil movement
- A collapsed section of old pipe
What to do now
What the plumber does
The plumber clears the main line through a cleanout, usually with a large cable machine sized for roots. Once water flows, a camera inspection shows what caused the backup and how far from the house it is.
If the camera finds roots in a cracked joint, a sag or a collapsed section, you'll get options from a spot repair to lining or replacement. A backwater valve can be added if the city main has ever surcharged into the house.
- Clear the main line
- Camera inspection
- Repair options for damaged pipe
- Backwater valve if needed
When to call a plumber
Call if the problem keeps coming back, if water is reaching walls, ceilings or electrical areas, or if any step above involves gas, a torch or opening a sewer line. A licensed plumber handles drain cleaning and will explain the cause before starting.
Questions
Will a backwater valve stop sewer backups?
Is a sewer backup covered by homeowners insurance?
This guide is general information for Colorado homeowners, not a substitute for an on-site diagnosis. Local codes vary; your plumber and building department have the final word.