What are the signs of a broken sewer line?

The short answer

A broken sewer line usually announces itself the same few ways: drains that clog again and again, several fixtures backing up together, sewage in the basement after a heavy rain, a sewage smell, and a wet or sunken spot in the yard over the line. Any one of these can have a smaller cause. Two or more together, or one that keeps coming back, are reason to have the line looked at with a camera.

Fairfax County lists the signs that a lateral may need repair as frequently clogged drains, odor of sewage, and basement backups during rain.^[1] The lateral is the private pipe from your house to the public sewer, and in the Virginia localities that publish a rule it is generally the owner's to fix; see who is responsible for the sewer line.

Signs inside the house

• The same clog keeps returning. One slow drain is usually a local clog. A main line that is cracked, offset or full of roots often catches paper and debris again soon after it is cleared. Our page on why a drain keeps clogging covers the local causes to rule out first.
• Several fixtures back up at once. When flushing a toilet makes the tub or a floor drain bubble or fill, the blockage is downstream of both, in the building drain or the lateral.
• The lowest drain overflows first. As the City of Salem puts it, "Backups will enter through the lowest drains first."^[4] A basement floor drain or shower that fills with dirty water is often the first place a main line problem shows.
• Backups during heavy rain. Fairfax County explains that rain-time basement backups happen because rain water is getting into the sanitary system, and the county lists root intrusion and cracked or broken laterals among the ways it gets in.^[1] If your basement backs up only in storms, your lateral may be one of those ways in.
• Gurgling. Toilets or drains that gurgle when other fixtures run can mean the line is partly blocked or air is moving through a break.

Signs in the yard

A leaking lateral leaves marks outside. When Fairfax County's code inspectors investigate a reported sewer leak, they look for dark colored liquid on the property or the street, soggy ground in the yard near the lateral, and sewage odors coming from one area of the property.^[1] They may ask the occupant to flush a toilet or run the tub for a few minutes and watch for gurgling sounds or bubbles coming from the soil.^[1]

Other things that can point to a leak along the line's path: a strip of grass that stays greener or grows faster than the rest, a depression or small sinkhole that was not there before, and a cleanout cap that is missing, cracked or wet around the base.

Is it your line or the public sewer?

When the backup happens matters. Fairfax County's guidance: "If the backup occurs only when facilities (such as toilet, tub, washer or sinks) are used, it is possible that you need a plumber."^[2] And: "If you have sewage backing up when you are not using any of your facilities, it is possible that there is a problem in the county main line."^[2] If neighbours are having the same trouble, or sewage is rising when no one is using water, call your sewer utility first.

Smells that are not a broken line

A sewage smell indoors is not always the sewer line. Fairfax County points out that "Sewer gas and odors could enter your home or business if any plumbing fixtures have not been used in a while and the water in the water-sealed traps has evaporated."^[2] Running water into a guest bath, a basement floor drain or an unused sink refills the trap. The county also notes that a vent plugged by leaves or a bird's nest can push sewer gas back into the house.^[2] If the traps are full and the smell stays, or it is strongest outside over the line, the line is the likelier source.

Why it should not wait

A cracked lateral rarely stays the same. Spotsylvania County explains that "Broken sewer laterals can allow tree roots or debris into the pipe, which may cause blockages, building backups, or overflows in the environment."^[3] Leaking pipes can also allow wastewater to reach groundwater,^[3] and a leaking lateral can wash soil away from around itself. If the cause is roots, see how to keep tree roots out of a sewer line.

Sewage is also a health hazard: Fairfax County warns that raw sewage can carry bacteria, viruses, molds and fungi.^[2] While you wait for help, stop running water, keep children and pets away from any wet area, and skip the drain cleaner. The City of Salem notes: "Chemical drain cleaners are not likely to help and can cause additional damage."^[4] If you must be near sewage, Salem's advice is plain: "Wear protective clothing such as rubber gloves, boots, and goggles."^[4]

How a plumber confirms it

The answer comes from a camera, not a guess. Fairfax County says: "The best way to assess the condition of a lateral is by Closed Circuit Television Video (CCTV) examination."^[1] The plumber feeds a camera through a cleanout or drain and records the whole run, which shows a crack, a root mass, a sag holding water, an offset joint or a collapse, and how far from the house it is. Ask for a copy of the recording. A sewer scope inspection can also be booked on its own, for example before buying an older house.

From there, the fix might be clearing roots, a spot repair, a liner or a full replacement. Our pages on what replacing a sewer line involves and what it costs explain the options.

When to call a licensed pro

Call a licensed plumber when more than one fixture backs up, the same clog keeps coming back, sewage reaches the basement, or you see wet, smelly or sinking ground over the line. Call right away if sewage is in the house. Diagnosing and repairing a sewer line means opening the line, handling raw sewage and often digging, and Virginia's plumbing contractor classification (PLB) covers the installation, maintenance, extension or alteration of sewerage systems.^[5] Check the licence before you hire: the Board for Contractors warns that a license number in an advertisement or on a business card does not necessarily mean the contractor's license is valid.^[6] Our guide to checking a contractor's licence shows how.

Get it looked at

Loclis lists licensed businesses from Virginia's DPOR register with their licence number and class. Browse sewer line services, look up plumbers in Blacksburg, or read more plumbing answers. If sewage is coming up now, describe the backup once and licensed local businesses respond.