If you've lived in Philadelphia long enough, you know the drill: a summer thunderstorm rolls through the Delaware Valley, dumps two inches of rain in an hour, and suddenly your basement has six inches of murky water — or worse, sewage. Sewer backups during heavy rain are one of the most damaging and unpleasant plumbing emergencies a homeowner can face, and they're far too common in the Philadelphia area.
The good news? Most sewer backups are preventable. Understanding why they happen and taking a few proactive steps can save you thousands in cleanup costs and protect your family's health. Here's everything you need to know.
Why Philadelphia Is Especially Vulnerable to Sewer Backups
Philadelphia's sewer infrastructure is among the oldest in the country. Large portions of the city — including neighborhoods like Fishtown, South Philly, Manayunk, and much of West Philadelphia — still rely on combined sewer systems. In a combined system, stormwater runoff and household sewage flow through the same pipes. During normal conditions, everything routes to the treatment plant. But during a heavy downpour, the system can't handle the volume.
When the combined sewer reaches capacity, the excess — a mix of rainwater and raw sewage — has to go somewhere. It either discharges into the Schuylkill and Delaware Rivers through overflow outlets or, in the worst case, backs up through the lowest drain in your home: typically a basement floor drain, toilet, or laundry sink.
Even homes in suburban areas like Media, Springfield, and Upper Darby with separate sewer systems aren't immune. Aging clay pipes, root intrusion, and undersized lateral lines connecting your home to the municipal main can all create bottlenecks that cause backups during storms.
Warning Signs a Backup May Be Coming
Sewer backups rarely happen without warning. Watch for these red flags, especially as storm season approaches:
- Gurgling sounds from toilets or drains when you run water elsewhere in the house
- Slow drains in multiple fixtures at the same time (not just one sink)
- Sewage odor coming from floor drains or basement fixtures
- Water marks or staining around your basement floor drain
- Toilets that bubble when the washing machine drains
If you notice any of these signs, don't wait for the next thunderstorm to find out the hard way. A professional sewer inspection can identify problems before they become emergencies.
7 Ways to Protect Your Home from Sewer Backups
1. Install a Backwater Valve
A backwater valve (also called a backflow prevention valve) is the single most effective protection against sewer backups. It installs on your main sewer line and allows wastewater to flow out of your home normally, but automatically closes if water tries to flow back in. During a storm, when the municipal system surcharges, the valve blocks sewage from entering your basement.
Philadelphia's plumbing code permits backwater valves, and some insurance companies offer premium discounts for homes that have them installed. The investment typically runs $1,500–$3,000 for professional installation — a fraction of what a single sewage cleanup costs.
2. Get a Sewer Camera Inspection
You can't fix what you can't see. A sewer camera inspection sends a high-definition camera through your lateral line to identify cracks, root intrusion, bellies (low spots where water pools), offsets, and buildup. For Philadelphia-area homes — especially those built before 1970 with original clay or cast iron pipes — this is one of the smartest investments you can make.
GenServ Pro recommends a camera inspection every 3–5 years, or immediately if you're experiencing any of the warning signs listed above.
3. Maintain Your Sewer Lateral
Your sewer lateral is the pipe that connects your home to the city's main sewer line, and in Philadelphia, it's your responsibility to maintain — all the way to the main. Many homeowners don't realize this. Tree roots, grease buildup, and deteriorating pipe joints are the most common problems we find in lateral lines throughout Delaware County and the Main Line.
- Root treatment: If you have mature trees near your sewer line, periodic root cutting or chemical root treatment can prevent blockages.
- Grease management: Never pour cooking grease down the drain. It solidifies in cool pipes and creates stubborn blockages that restrict flow exactly when you need capacity most.
- Professional cleaning: Hydro jetting every few years clears buildup and restores full pipe diameter.
4. Upgrade Your Sump Pump System
If your basement has a sump pit, your sump pump is your first line of defense against groundwater during storms. Make sure it's up to the task:
- Test it before storm season by pouring water into the pit and confirming it activates
- Install a battery backup — power outages during storms are common in the Philly area, and your pump is useless without power
- Consider a water-powered backup pump for an additional layer of protection
- Replace pumps older than 7–10 years, even if they still seem to work
5. Disconnect Downspouts and Sump Pumps from the Sewer
In many older Philadelphia homes, roof downspouts and sump pump discharge pipes are connected directly to the sanitary sewer line. This means every rainstorm sends hundreds of gallons of stormwater into an already-stressed system. Disconnecting these and redirecting water to your yard, a rain garden, or a dry well significantly reduces the load on the sewer system — and your risk of a backup.
Philadelphia Water Department actually encourages this through their Green City, Clean Waters program, and some municipalities offer incentives for stormwater management improvements.
6. Seal Basement Cracks and Openings
Stormwater doesn't just enter through drains. In many Philadelphia row homes and older colonials, water seeps through foundation cracks, gaps around pipe penetrations, and deteriorated window wells. Sealing these entry points with hydraulic cement, exterior waterproofing membrane, or proper window well covers reduces the volume of water that reaches your basement during heavy rain.
7. Know Where Your Cleanout Is
Every home should have a sewer cleanout — a capped pipe that provides direct access to your main sewer line. In an emergency, a plumber can use the cleanout to quickly clear a blockage or relieve pressure. Many Philadelphia homeowners don't know where theirs is (or if they even have one). It's typically located near the front of the house, either inside the basement or just outside the foundation wall. If you can't find yours, GenServ Pro can locate it or install one if needed.
🚨 What to Do During an Active Sewer Backup
If sewage is actively backing up into your home: don't use any water fixtures. Don't flush toilets, run sinks, or start the washing machine — this adds more water to an already overwhelmed system. Avoid contact with the backup water, which contains harmful bacteria. If the backup is severe, turn off electricity to the basement at the breaker panel (from upstairs, not while standing in water) and call a plumber immediately.
Does Homeowner's Insurance Cover Sewer Backups?
Here's something that surprises many Philadelphia homeowners: standard homeowner's insurance policies typically do not cover sewer backup damage. You usually need a separate sewer backup endorsement or rider, which costs $40–$100 per year and provides $10,000–$25,000 in coverage. Given that professional sewage cleanup and restoration can easily exceed $10,000, this rider is well worth adding to your policy.
Talk to your insurance agent about adding sewer backup coverage before storm season hits. And if you've already installed a backwater valve, mention it — you may qualify for a discount.
When to Call a Professional
Some preventive measures — like disconnecting a downspout or testing your sump pump — are straightforward DIY tasks. But for the following, you'll want a licensed plumber:
- Backwater valve installation (requires cutting into your main sewer line)
- Sewer camera inspection and line cleaning
- Sump pump installation or replacement
- Root removal and hydro jetting
- Sewer lateral repair or replacement
- Any active sewage backup situation
GenServ Pro is licensed (PA HIC # PA 056854) and equipped to handle everything from routine sewer maintenance to emergency backup situations throughout Philadelphia, the Main Line, and Delaware County. We've seen what summer storms do to aging sewer systems in this area — and we know exactly how to protect your home.
Don't Wait for the Next Storm — Protect Your Home Now
Schedule a sewer inspection or backwater valve consultation with GenServ Pro. We serve Philadelphia, the Main Line, and all of Delaware County with fast, professional service.