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Sewer backup: Paddling into flood insurance insights

For policyholders and insurers alike, water in a home is often not a welcome sight. And it’s a growing problem, especially from an emerging risk: Sewer backups.

The more you know about a property’s water exposure, the more accurately you’ll be able to underwrite that specific property.

The numbers are illuminating when evaluating the emergence of sewer backup risk and the related causes – including aging municipal lines and weather-related influences.

  • The rate of sewer backup incidents is increasing by 3 percent annually1.
  • The average sewer line is more than 30 years old2.
  • 62 million residential locations are at moderate to extreme risk of flooding3 and potentially, by extension, sewer backups.

Backups can have multiple causes, including municipal systems being overwhelmed by a temporary spike in public use or a discharge of home wastewater blocked by an obstruction and returned into the home. But another notable source of risk is weather-related: Flash floods can also overwhelm municipal sewer systems—regardless of age or state of repair.

Whatever the cause, the results can be complicated, from immediate property damage that can linger and lead to costly claims to health hazards for the homeowner. The more you know about a property’s water exposure, the more accurately you’ll be able to underwrite that specific property. And from an insurance policy standpoint, what constitutes a non-weather water event, such as sewer system defects vs. homeowner accident—an overflowing washing machine, for example—can be challenging to settle.

Coverage is evolving

In the past, both carriers and agents have shared the need in the industry to broaden the level of coverage for events that lead to water inundating a home. And the coverage situation is changing with the addition of an optional, broadened water backup and sump discharge/overflow endorsement.

Previously the water backup coverage in the ISO Homeowners Program included water that originated from within an insured’s home and backed up through sewers and drains or came from equipment such as a sump pump. ISO’s new option eliminates the limitation that a water backup must originate from within the dwelling. As a result, it also broadens the water sources covered in the current program to not be limited to water originating from within the home.

Tools of the trade

Because flooding events can also influence sewer backup, flood risk analytics can help you better understand your policyholders’ exposure. These analytics, which use advanced river, surface, and storm-surge flooding models to score an area’s risk of a notable flood event, can help underwrite policies accordingly. They also include address-level information regarding potential exposure to floods based on the amount of rain they receive over a specific time period.

Verisk’s flood solutions can help you keep your customers informed—even those in areas not traditionally considered flood-prone—with critical information about a property’s exposure to flooding.

When you’re confronting perils like a sewer backup, even where robust infrastructure data is lacking, understanding both coverage and related weather factors can help you better understand and account for your policyholders’ exposure. By using flood analytics to understand potential risk factors, you can do more to account for a water damage event, even if not strictly weather-related, such as sewer backups.

Learn more about Verisk’s solutions for flooding and sewer backups.

Brian Snyder

Brian Snyder is product specialist at Verisk. He can be reached at

William C. Schlager

William C. Schlager is director of personal property and farm product development, Underwriting Solutions at Verisk. He can be reached at

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  1. The Civil Engineering Research Foundation, 2021.
  2. The American Society of Civil Engineers, 2021.
  3. Verisk data, 2021

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