Water backup and sewer backup coverage

A standard homeowners policy does not cover water that backs up through a sewer or drain, or that overflows from a sump pump. You add that protection with a water backup endorsement (ISO form HO 04 95 and its many insurer-specific equivalents). It is cheap compared with most coverage, and it usually comes with a modest limit that appears on your declarations page. A flood insurance policy does not fill the gap either, except in the narrow case where an area-wide flood causes the backup.

What the base policy excludes

The ISO HO-3 (form HO 00 03, 2011 edition) excludes loss caused by "water which backs up through sewers or drains" and by water that "overflows or is otherwise discharged from a sump, sump pump or related equipment." It does so "regardless of any other cause or event contributing concurrently or in any sequence to the loss," so it does not matter whether a tree root, a heavy rain or a municipal overload started the chain. Most insurers' forms follow the same logic. The relevant glossary entry is water damage exclusion.

The same form does cover water that comes out of your plumbing or an appliance, which is the opposite direction of flow. The distinction is physical. Water that comes out of a supply line is a plumbing loss. Water that comes up through the floor drain is a backup, and it is excluded. See is water damage covered by homeowners insurance? for how the two sit side by side.

What the endorsement adds

The ISO endorsement is titled Water Back-Up and Sump Discharge or Overflow. It adds back coverage for water or waterborne material that backs up through sewers or drains, or that overflows or is discharged from a sump, sump pump or related equipment. Four features matter more than the title.

It is a sublimit. The endorsement does not increase your Coverage A through D limits. It sets a separate cap on the most the insurer will pay for this kind of loss, shown on the declarations page. In the North Carolina version of the ISO endorsement (HO 04 84), a 2010 North Carolina Rate Bureau circular described a basic limit of $5,000, which could be increased to $10,000, $15,000 or $25,000; before that change the endorsement had paid up to the policy limits. Other states and insurers set their own options. One AAA club insurer's filed endorsement (form CO 04 95, 11 03 edition) sets a $5,000 limit and a special $500 deductible. Those are examples from specific filings, not a national schedule.

It carries its own conditions. The North Carolina notice and the AAA form both cover direct physical loss "not caused by the negligence of" an insured. That wording matters in a claim where the owner ignored repeated backups or a known root problem. The AAA form does not pay for the sump pump itself or related equipment when it fails because of breakdown. It pays for the water damage the overflow causes, not the machine.

Flood still isn't covered. The endorsement replaces the water exclusion only for backup and sump discharge. Flood and surface water stay excluded. If rising floodwater pushes sewage up through a drain, the cause is flood, and that is a flood policy question.

Details vary. Wording differs on points such as whether a backup that starts in the municipal main is covered, how the deductible works and whether a sump pump that stops during a power outage is included. Ask your agent for the edition and form number and read the endorsement itself. The sump-specific issues are covered in sump pump failure and basement flooding.

Why a flood policy usually doesn't help

The National Flood Insurance Program's standard policy, as written in federal regulation, excludes "water or water-borne material that: backs up through sewers or drains; discharges or overflows from a sump, sump pump, or related equipment; or seeps or leaks on or through the insured property," unless "there is a flood in the area and the flood is the proximate cause" of the backup, sump overflow or seepage (44 CFR Part 61, Appendix A(1), Article V%20to%20Part%2061)). The policy also defines flood as general and temporary inundation of two or more acres or two or more properties. A blocked lateral on your lot, tree roots, grease in the city main or a failed sump pump will not meet that definition. For the full picture, see NFIP flood insurance explained and does homeowners insurance cover flooding?.

Whose pipe is it?

Backups come from two places, and ownership decides who may be responsible beyond your insurer.

• The lateral, the pipe from your house to the sewer main, is normally the property owner's. In Gwinnett County, Georgia, for example, the water department states that the owner is responsible for the maintenance and operation of the sewer lateral, up to and including the connection with the public sewer, and that if a backwater valve is required by code and missing, the county is not responsible for damage from a main backup. Rules differ by city and county, so ask your sewer utility.
• The main, the public sewer under the street, belongs to the municipality or sewer district. When a storm overloads it and sewage comes up in basements, homeowners often assume the city will pay. Municipalities often have legal protections and strict notice requirements for claims, so do not count on it; a claim under your own endorsement is usually faster.

The endorsement pays for the damage the water does inside your home. It does not pay to repair or replace the lateral. That falls under service line coverage for water, sewer and power lines, a separate endorsement that covers underground utility lines on your property, again with a stated limit.

Choosing a limit (a hypothetical example)

Basement backups can be expensive because of what sits at floor level and because sewage-contaminated materials are typically removed rather than dried. Say you have a finished basement and the drain backs up. The following figures are invented for illustration:

With a $5,000 backup limit and a $500 deductible, the policy would pay about $4,500 of that $55,000. With a $25,000 limit, it would pay about $24,500. The difference in what you collect is large, so ask your agent what the step up in limit costs; pricing varies by insurer, state and limit. Also ask whether the limit applies per occurrence or per policy year. Add up what is in the lowest level of your house, not your whole house, and set the limit against that number. The homeowners coverage gap checker tool helps frame the question.

When a backup claim gets denied

• No endorsement. The most common reason. Check the declarations page for "water backup," "sewer backup," "backup of sewers and drains" or similar.
• Negligence or a known problem. An insurer may point to prior backups, an ignored plumber's warning or missing maintenance.
• Flood as the cause. If rising water outside the house triggers the backup, expect the flood exclusion to be raised.
• The limit. The claim is paid, but only to the sublimit.
• Equipment. The failed pump, valve or pipe is not part of the covered loss.

If you disagree with a denial, ask for the specific policy language in writing and see homeowners claim denied: what to do next.

If sewage comes up: a short sequence

1. Stop using water in the house and keep people and pets out of the affected area. Sewage contamination is a health hazard.
2. Call a plumber to clear the line and, if possible, run a camera inspection. A video showing roots, a collapsed pipe or a blockage in the main establishes the cause.
3. Call your sewer utility. Ask whether other homes on the street are affected, and record who you spoke with.
4. Photograph and video everything before cleanup, and keep a list of what is damaged.
5. Report the claim, and hire a restoration company with the right equipment and protective gear. Save receipts. See the first 48 hours after damage to your home.

Reduce the odds

A backwater valve, installed on the sewer line and maintained, blocks reverse flow from the main. Some codes require them for homes with fixtures below the street sewer. A periodic camera inspection of an older lateral, keeping roots and grease out of the line and knowing where your cleanout is will help, as covered in water damage prevention: a homeowner's checklist. If your basement is finished or holds a laundry room, treat the endorsement as one of the cheaper coverages you can add.

Key takeaways

• Sewer and drain backup and sump overflow are excluded by the standard HO-3; the water backup endorsement adds them back as a sublimit.
• The limit is separate from your dwelling limit and is often a small number, so set it against the value of your lowest level.
• NFIP flood coverage applies to a backup only when an area-wide flood is the proximate cause.
• You own the lateral in many places; the endorsement pays for the water damage, not for fixing the pipe.
• Ask your agent for the form number, limit, deductible and whether municipal main backups are included.