Sewer Backups in Atlanta: Why Older Intown Houses Take Sewage Back

Why do older Atlanta houses take sewage back through the floor?

In older parts of the city the street sewer carries rain and household waste together. A heavy downpour fills it faster than it empties, so the level rises in the pipe and finds the lowest opening, usually a floor drain, a basement toilet or a shower. Roots and aged lateral pipes make it worse.

The mechanism is plain physics. Your house drain slopes downhill into a lateral, which joins the main in the street. In dry weather the main runs part full. In a hard storm the main fills, then pressurizes, and the level in the pipe can climb above the lowest fixture in your house. That fixture becomes the relief valve. A basement floor drain, a laundry tub or a ground-floor toilet on the low side of a hill is where the sewage arrives.

Atlanta's intown housing makes this more likely in a few ways. The 1920s to 1950s bungalows of the east and west sides often have basements or low ground floors, plus original cast-iron or clay drain lines that are decades old. In older houses these lines commonly develop cracks, offset joints and root intrusion, a general pattern rather than a survey result. Big trees on big lots, the reason Atlanta is called a city in a forest, push roots into those joints. Cascade Heights, with the second densest canopy in the city, is a clear example of where that pattern applies.

Atlanta's red Piedmont clay adds to the problem on the outside of the pipe. Clay soil drains slowly, so storm flows run off hillsides and into the street system instead of soaking in. Paving does the same thing downtown, which is why creeks that begin in the middle of the city, such as Intrenchment Creek and Proctor Creek, send heavy flows into neighborhoods downstream.

None of this tells you whether a particular street or house has a combined sewer, and this guide will not claim it. The utility for your address can say what kind of sewer serves you, and a licensed plumber can scope the lateral with a camera.

What is Atlanta's combined sewer system, and what did the consent decrees change?

A combined sewer carries sewage and stormwater in one pipe and is built to spill to a creek when rain exceeds its capacity. Atlanta has been under federal consent decrees since 1998, with a companion in 1999. The city built seven control facilities in the mid-1980s and early 1990s, and by 2000 controls had cut overflow volume about 60 percent.

Combined sewers were a design of their era. A single pipe was cheaper than two, and in dry weather it worked. The weakness is that a storm can send more flow than the pipe or the treatment plant can take, and the relief is an overflow structure that discharges diluted sewage into a creek. The U.S. EPA has a long-running national program to control combined sewer overflows, and Atlanta was one of the cities under it.

A 1998 federal consent decree placed Atlanta's sewer system under federal oversight, followed by a companion decree in 1999. Before that, the city had built seven combined-sewer overflow control facilities between the mid-1980s and the early 1990s, and by 2000 EPA reported that controls had cut combined-sewer overflow volume about 60 percent and solids loading about 75 percent. Intrenchment Creek has one of those facilities, on Custer Avenue SE, built in the mid-1980s with the East Area system. A 1997 decree limits the combined sewage it may discharge.

What the decrees do not tell you is what happens inside any one house. They govern what leaves the system at the outfall and how fast the city repairs and separates pipes. They do not stop a surcharging main in a storm from finding the lowest drain in a home, and they do not describe which blocks have been separated. This is why a homeowner who has never had a backup can still have one, and one who has had it may not have it again.

Which parts of Atlanta have a documented sewage problem?

The documented record includes sewage in houses in Vine City and English Avenue, persistent flooding and combined overflows along Intrenchment Creek, a 2018 spill into Utoy Creek near Cascade Heights, overflows into the South Fork of Peachtree Creek near Tucker and an airport lift-station spill into Sullivan Creek. None of these says your street is affected.

The table below lists where public records and news coverage describe sewage problems. It is a map of reported patterns, not a prediction for an address, and a quiet neighborhood is not a guarantee. If you live in one of these areas, it is worth knowing the pattern. If you do not, a backup is still possible anywhere an old lateral meets a surcharging main.

The strongest local pattern is in the west, around Vine City and English Avenue in the Proctor Creek watershed. For decades heavy rain flooded streets and homes there, overwhelmed aging sewers and in some cases pushed raw sewage into houses. The city has since built green infrastructure along Boone Boulevard, including Cook Park, which stores runoff in retention ponds. The local lesson is that sewer backup, not just surface water, is the thing to plan for.

How do you tell whether the blockage is yours or the city's?

If several drains fail at once, the lowest fixtures back up first, and it happens during or right after heavy rain, the street main is the likely cause. If one fixture backs up in dry weather, your own lateral is more likely. The sewer utility and a licensed plumber are the two calls that settle it.

The pattern is a clue, not proof. A backup on a rainy night that clears when the storm ends points at a surcharging main. A backup on a sunny afternoon that returns when you run the washing machine points at a blockage or a root mass inside your own pipe. A camera inspection by a plumber shows the difference, and it is plumbing work, not restoration work.

Who the sewer belongs to depends on the address. Inside the City of Atlanta, sewer and stormwater are run by the Department of Watershed Management. In DeKalb County the DeKalb County Department of Watershed Management runs water and sewer, and the county, not the city of Tucker, handles sewer problems there. Cobb, Clayton and Douglas counties each have their own water authorities. Confirm yours before you call.

Ask the utility whether the main near your house is surcharging or has been reported. Ask a plumber whether a backwater valve is appropriate for your line. A backwater valve is a plumbing fixture that closes to stop flow from reversing, and it is a decision for a licensed plumber, not something a restoration crew installs.

For the cleanup itself, our sewage backup cleanup page explains how a crew works, and the guide on creek flooding in Atlanta covers the case where the water came from outside instead of through the drains.

What must be thrown away after a sewage backup, and what can be saved?

Porous materials that sewage has soaked, such as carpet, pad, insulation, drywall, mattresses and upholstered furniture, are generally removed and discarded. Hard nonporous surfaces such as tile, sealed concrete and metal can usually be cleaned and disinfected. Wood and cabinets are a judgment call that a technician makes with moisture readings.

Sewage is Category 3 water under the ANSI/IICRC S500 standard: grossly contaminated, carrying bacteria, viruses and parasites that can make people ill. That is the reason the usual drying approach does not apply. Drying a porous material removes the water but leaves the contamination behind, so the material is taken out instead.

The line between discard and save follows how a material absorbs. A basement floor drain that backs up and covers a concrete floor is one scenario. A backup that soaks wall-to-wall carpet, runs under a finished wall and wicks up drywall is another. The technician looks at how high the water reached and how long it stood, then marks where the cuts go, usually a short distance above the visible line, because wicking carries moisture higher than the eye can see.

Anything you keep, you keep on the crew's advice. Do not decide on your own that a sofa, a rug or a stack of boxes in a cardboard carton is fine because it looks dry. Cardboard and paper are porous and sewage leaves little visible trace on them.

What should you not do after sewage comes up through a drain?

Do not walk through it barefoot or in street shoes, do not run a household wet vacuum on it, do not keep running water that drains into the same line, and do not mix bleach with other cleaners. Keep children, pets and anyone with a weak immune system out, and call a crew trained for Category 3 water.

The urge to start cleaning immediately is natural, and it is where most avoidable harm happens. Sewage is not dirty water. It is a biological hazard, and the way you handle the first hours decides how much of the house can be saved and how safe it is to live in.

• Stay out of standing water near outlets, cords and appliances, and cut power to the area only if you can reach the panel without wading.
• Do not use a household wet vacuum. It pulls contamination into a machine that cannot be sanitized and can throw fine droplets back into the room air.
• Do not flush toilets or run the washer and dishwasher while the line is backing up. Every gallon you add goes to the same blocked line and ends up on the floor.
• Do not mix bleach with ammonia or other cleaners, because the combinations can release dangerous fumes. Ventilate if you use any disinfectant.
• Do not try to dry carpet, pad or drywall that sewage touched. Dry-looking is not clean.
• If you must go in, wear rubber boots, waterproof gloves and eye protection, and wash your hands and clothes afterward. Keep children and pets out.
• Photograph the water line and the damage before anything is moved, and call your insurer early.

What does a sewage backup cleanup involve, and will insurance pay for it?

A crew extracts the sewage, removes porous materials, cleans and disinfects hard surfaces, then dries the structure and checks moisture until it reads dry. Insurance depends on your policy: standard homeowners coverage generally excludes sewer and drain backup unless an endorsement was added, so check your policy and ask your agent.

The sequence is the same every time, even though the scale varies. First comes the extraction of standing sewage with equipment built for it. Then removal of the materials listed above, bagged and carried out without dragging them through clean rooms. Then cleaning of hard surfaces and structural framing, followed by antimicrobial treatment. Last comes drying with air movers and dehumidifiers, with moisture readings repeated until the structure is dry. A basement can need much of this carried out from the bottom up, because the lowest point is where the sewage settled.

Repairs to drywall, trim and flooring are a separate stage and are quoted after drying. The emergency stage is explained and approved before work begins, and you can ask for photos and moisture readings to share with your insurer.

On cost, this guide gives no sewage figure because no Atlanta-sourced one exists. Read how water damage restoration pricing works in Atlanta for the sourced ranges and how to read an estimate.

On insurance, the Georgia Commissioner of Insurance has said a home policy covers wind and fire basically and that flood is a separate matter. Sewer and drain backup commonly sits behind an endorsement. If you have flooded before, ask your agent now what your policy says, because the answer is far less useful in the middle of a loss. No one can promise that a claim will be paid, and we will not.