A tornado watch covering more than 32 million people and flash flood warnings across New Jersey and Pennsylvania dumped up to three inches of rain in a single afternoon this week, flooding streets and shutting down NJ Transit's River Line. Here is what that kind of storm does to a home's plumbing, and how to get ahead of the next one.
A Rough Afternoon Across the Region
On July 21, 2026, the National Weather Service issued a tornado watch covering more than 32 million people from Delaware through Philadelphia, New Jersey, New York City, and into Connecticut, warning of wind gusts up to 70 miles per hour and hail as large as ping pong balls. A flash flood warning followed for the Philadelphia region as rain fell at one to two inches per hour during the heaviest bands.
New Jersey saw all 21 counties placed under a flood watch, with up to three inches of rain reported in parts of the state. NJ Transit suspended River Line rail service in both directions after floodwater covered the tracks near the Waterfront Entertainment Center in Camden, and street flooding was documented at intersections in Philadelphia, including standing water deep enough that pedestrians had to wade through it.
Why This Turns Into a Plumbing Problem, Not Just a Weather Story
When rain falls faster than storm drains can carry it away, the excess has to go somewhere, and in many older NJ and PA municipalities the storm sewer and the sanitary sewer share the same pipe. During a heavy downpour like this week's, that combined system can fill to capacity and push wastewater backward through the path of least resistance, which is often a basement floor drain, a laundry tub, or a low toilet.
Even in newer separated systems, a home's own sanitary lateral can back up if tree roots, grease, or age have narrowed the pipe, because the sudden surge of rainwater raises groundwater levels around underground pipes and adds pressure from the outside. Either way, the result at the house level looks the same: water coming up rather than draining down.
The Two Upgrades That Actually Matter
A backwater valve, sometimes called a check valve, installed on the sewer lateral where it leaves the house lets wastewater flow out but closes automatically if water tries to flow back in. It is one of the few plumbing fixes that specifically targets sewer backup rather than general flooding, and it is worth having a licensed plumber assess if your home has ever taken on water during a heavy storm.
A sump pump handles a different job, moving groundwater that seeps into a basement or crawl space out and away from the foundation before it accumulates. The catch is that storms like this week's often knock out power exactly when the pump is needed most, so a battery backup or water powered backup system is what actually keeps the pump running through the worst of the event.
What to Do If Water Already Got In
Water that backs up through a drain during a storm should be treated as contaminated, since it has likely mixed with sewage or street runoff, even if it looks clear. Avoid direct contact where possible, keep kids and pets away from the area, and skip running washing machines or dishwashers during an active flood warning, since that adds volume to a system that is already struggling to keep up.
Once the water recedes, a wet vacuum can remove standing water, but soaked drywall, carpet, and insulation near a sewer backup usually need to be removed rather than dried out. If you are dealing with recurring backups rather than a one time storm event, that is a sign to have a plumber camera-inspect the lateral line rather than just cleaning up after each storm.
Figures reported by the National Weather Service and regional transit officials for the July 21, 2026 storm.
6 Ways to Flood Proof Your Home's Plumbing Before the Next Storm
You cannot stop three inches of rain in an afternoon, but you can control how much of it ends up in your basement. Start here.
- Install a backwater valve: This is the single most effective defense against sewer backup during a heavy storm, and it pays for itself the first time it stops wastewater from flowing back into your basement.
- Add a battery backup to your sump pump: A sump pump that loses power during the storm it was installed for is not protecting anything. A battery or water powered backup keeps it running through an outage.
- Clear gutters and downspouts before storm season: Clogged gutters send rainwater straight down your foundation instead of away from it, adding to the groundwater pressure that pushes into basements.
- Grade soil away from the foundation: Soil that slopes toward the house instead of away from it funnels every storm's runoff right to your basement walls.
- Hold off on laundry and dishes during a flood warning: Running extra water into an already stressed sewer system during a warning increases the odds of a backup at your house or your neighbor's.
- Know your main shutoff and cleanout locations: In an active backup, being able to find your sewer cleanout quickly gives a plumber a faster way to relieve pressure and diagnose the blockage.
Frequently asked questions
- Should I avoid using water in my house during a flood warning?
- It's a good idea to hold off on non-essential water use like laundry and dishwashing during an active flash flood warning, since it adds volume to storm and sewer systems that may already be at capacity.
- What is a backwater valve and do I need one?
- A backwater valve is installed on your sewer lateral and closes automatically to stop wastewater from flowing back into your home during a surcharge event. It is worth considering if your home has ever flooded from a drain rather than a window or door.
- Is floodwater coming up through a drain a plumbing emergency?
- Yes. Water rising through a floor drain or toilet during a storm should be treated as a plumbing emergency and likely contaminated water, not just a housekeeping issue, and is worth an emergency call rather than waiting until morning.
- Does homeowner's insurance cover sewer backup?
- Standard homeowner policies typically exclude sewer and drain backup unless you've added a specific endorsement or rider, which is worth checking with your insurer well before the next storm rather than after one.