How to tell it is the main line
- Water comes up the basement floor drain when the washer drains or a toilet flushes.
- The toilet bubbles when the tub drains.
- Every fixture on the lowest floor is slow at the same time.
- You can smell sewage near the floor drain.
The floor drain is the lowest opening in the house, so it is where a blocked main shows itself first. Stop running water until the line is open. Whatever you send down a drain upstairs comes back up in the basement.
How the line is cleared
A main line is cleaned through a cleanout, a capped access pipe usually found in the basement floor near the front wall, at the base of the stack, or out in the yard. A heavy cable with a cutting head is run from the cleanout toward the street, far enough to reach the public main. The head is sized to the pipe so it scrapes the full width and doesn't just open a small hole through the middle.
Some older homes have no usable cleanout. The line is then reached through a stack access inside the house if there is one, and by pulling a toilet if there isn't. It takes longer. If your line needs cabling regularly, ask about having a cleanout installed.
Backups during heavy rain
Much of the City of St. Louis, the Central West End included, and some of the inner suburbs are on combined sewers, where storm water and sewage share one pipe. In a hard rain the public sewer can fill and push back through basement floor drains.
If your drain only backs up during storms, and the neighbors have the same trouble, the blockage may not be in your line at all. MSD will check the public main when a backup is reported. If the main is clear, the problem is in your lateral.
Low ground near a river can do the same thing without a combined sewer. Parts of Arnold along the Meramec back up when the river is high. In both cases the usual fix is a backwater valve on the lateral, not a cable.
Who to call about the public main
It depends on where you live. MSD runs the public sewers in the City of St. Louis and most of St. Louis County, and takes backup reports around the clock at 314-768-6260. Across the river in St. Charles County the cities and sewer districts run their own. St. Peters publishes a test for telling the city's problem from yours. O'Fallon addresses are split between the city and the Duckett Creek Sanitary District. Arnold's sewers belong to Missouri American Water.
What usually blocks a main line here
Where the line outside is clay, it is roots. Clay tile has a joint every few feet, and tree roots find them.
Wipes and tampons are the other leading cause. In a sound pipe they usually pass. In a pipe with a rough, rotted wall or a belly, they catch and build into a plug.
Cabling clears all of these for a while. If the line clogs again inside a year, get a camera inspection so you know which one you have. Roots call for cutting on a yearly schedule. A flat line that keeps collecting debris calls for jetting on a schedule.
Cast iron under the house
Most cast iron drain pipe in older homes here is past its service life. When it is the cause, the usual order is to descale the pipe, flush it, and inspect it by camera. What the camera shows decides between lining and digging it up.
Common questions
Should I call the sewer district or a drain company first?
If the backup only happens when you run water, the blockage is almost always in your own line, and that is a drain cleaning call. If sewage comes up when nobody in the house is using water, or the neighbors are backing up too, call your sewer provider first, because the public main may be blocked. In the City of St. Louis and most of St. Louis County that is MSD, at 314-768-6260.
How much does main sewer line cleaning cost?
Service work is $240 an hour. A line with a usable cleanout goes faster than one that has to be reached through a stack or by pulling a toilet. If a camera is used during the visit, add $60.
Can I use the water while I wait?
Use as little as you can. While the main line is blocked, every gallon sent down a drain comes back up at the lowest opening in the house, which is usually the basement floor drain. Hold off on laundry, the dishwasher and showers until the line is open.
Does homeowner's insurance cover a sewer backup?
Usually only if the policy has a sewer backup endorsement, which most insurers sell as an add-on. MSD says its own programs don't cover a backup caused by a private lateral. Ask your agent what your policy covers before you need it.