Overflow during storms

Quick Answer:

If a toilet overflows during heavy rain, stop flushing and stop using water in the house. Storm-time backups usually mean the public sewer or a saturated collection system is overloaded (a sewer surcharge). Wait to see if water recedes after the storm slows; recovery can take a few hours to a day. If backups continue, call a plumber experienced with sewer backups.

Why This Happens

During heavy storms the municipal sewer or your local collection main can become full from excess rainwater. When the system is overloaded it can push sewage and stormwater back into the lowest fixtures—often toilets, floor drains, and basement drains. This is called a sewer surcharge. If multiple drains back up at once or water appears from unexpected places, that pattern points away from a single clogged trap and toward an external surcharge.

Step-by-Step What to Do

1. Stop using water immediately

• Do not flush toilets, run sinks, showers, washing machines, or dishwashers.
• Shutting off water use prevents more sewage from entering an already stressed system and reduces the chance of additional backups.

2. Contain and protect your space

• Block off the area around the overflow to keep children and pets away.
• Place buckets or towels to limit spread. Remove rugs and fabric items that can absorb contaminated water.

3. Watch recovery time

• Note how long it takes for water levels to drop—many surcharge events clear within a few hours after rainfall decreases, but some can take up to 24–48 hours.
• Document timing and photos if you plan to report the issue to the utility or a plumber.

4. Check other fixtures

• Carefully check other low fixtures (basement floor drains, laundry drain, other toilets). If multiple fixtures show backup, that strongly suggests a sewer surcharge rather than a single clog.
• If only one toilet overflows and the trap drain is clear, see Toilet overflows but drain not clogged for other causes.
• If water is coming up from drains without an obvious blockage, see Overflow with no visible blockage.

5. Clean up safely when water recedes

• Once levels are back to normal, remove contaminated materials, disinfect affected hard surfaces with appropriate cleaners, and launder washable items separately.
• If sewage contacted carpets or upholstery, consider professional cleaning or replacement depending on contamination level.

What Not to Do

• Don’t flush during storms if overflow occurs—sewer surcharge risk; a plumber is appropriate.
• Do not attempt to snake or open a sewer cleanout if the system is surcharged; tools or opening the line can release contaminated water and create hazards.
• Do not enter standing sewage or try to clean large sewage volumes without protective gear and proper disinfectants.

When to Call a Professional

• Multiple fixtures are backing up at the same time.
• Sewage is in the basement or in areas with large volumes of wastewater.
• Backup continues more than 24 hours after the storm has passed, or keeps recurring with each rain.
• You smell strong sewer gases, see manhole overflow nearby, or suspect damage to your sewer line.

A licensed plumber can inspect the home plumbing, check the cleanout, advise whether the public sewer is affected, and coordinate with the local utility if needed.

Safety Notes

• Treated or untreated sewage is a health hazard. Wear gloves, boots, and eye protection when handling contaminated materials.
• Open wounds should be kept away from contaminated water; seek medical attention if exposed to raw sewage.
• Avoid mixing household cleaners (especially bleach and ammonia) when disinfecting—mixing chemicals can create toxic fumes.
• Call local authorities if you see persistent surcharging of public manholes or large street/yard flows—these are utility issues that can affect neighbors.

Common Homeowner Questions

For more related articles, see the Kitchen Sink Overflows & Sudden Backups hub.