What a belly is

Gravity sewer laterals depend on a continuous downhill slope from the house to the main. A belly is a stretch where the pipe dips below that line, so water settles in the low point instead of draining away. Solids drop out of the slow water and build up, and the next clog often starts there.

Bellies can come from soil settling under the pipe, poor bedding when the line was installed, nearby digging, or the weight of a structure or driveway over it. Some are shallow and cause little trouble. Others hold enough water that the camera goes completely under.

Quick facts

How it shows
The camera dips into standing water that stays in one stretch.
Main effect
Solids settle, leading to repeat clogs.
Often found with
Offset or separated joints at either end of the sag.
Hard to judge
How deep the sag is; ask how it was estimated.

Signs you might have a belly

  • Clogs that come back at the same footage each time the line is cleared.
  • A cleaning cable that comes back coated in sludge rather than roots.
  • Slow drainage throughout the house even after cleaning.
  • Gurgling after large volumes of water, such as a tub draining.
  • A camera picture that disappears underwater partway down the line.

How a plumber evaluates a sag

  1. Note where water starts and stops.The footage at the start and end of standing water gives the length of the low section.
  2. Watch how deep the camera goes.If the lens is partly or fully submerged, that indicates how much water the section holds.
  3. Check the joints on either side.Sags often pull joints out of line, which can let roots in and catch debris.
  4. Locate the low point.Marking the sag on the ground shows whether it sits under lawn, a driveway or the slab.
  5. Re-run after flushing.Running water and filming again can show how the section drains over time.

Living with a belly versus correcting it

Manage it

  • Periodic cleaning to clear settled solids
  • Can be reasonable for a short, shallow sag
  • Track how often clogs return
  • Re-inspect to see if it is getting worse

Correct it

  • Re-lay or replace the sagging section at proper slope
  • Lining generally follows the existing sag
  • Excavation depends on where the low point is
  • Ask what slope the repaired section will have

Questions to ask

  1. How long is the low section, and how much water does it hold?
  2. Is the sag causing the clogs, or is something else involved?
  3. Is the low point under concrete or open ground?
  4. Would you recommend managing it or correcting it, and why?
  5. Can I have the footage of that section to share with another plumber?

Common questions

Is a little standing water in a sewer line normal?

A small amount at a fitting or a slight dip can be minor. A long stretch of water or one that submerges the camera is more significant. Ask how your footage compares.

Can hydro jetting fix a belly?

Jetting can clear settled solids from a sag, but it does not change the slope of the pipe. The low spot remains.

Why did my line develop a sag?

Common causes include settling soil, original installation and later digging nearby. A plumber can describe what the footage suggests but may not be able to confirm the cause without excavation.

General information for Fullerton, not a quote or professional advice. In an emergency, call 911.