Guides
Sump pump failure and basement flooding
Sump pump failure, groundwater and surface water are excluded from a standard homeowners policy. What an endorsement or flood policy adds to a basement.
A standard homeowners policy does not pay for basement water caused by a sump pump that fails, overflows or is overwhelmed. That is true whether the pump quit because of a dead motor, a stuck float or a power outage. Coverage comes back only if you added a water backup and sump discharge endorsement, and even then it is usually a limited sublimit that does not pay for the pump itself. Groundwater seeping through the floor and rainwater coming in through window wells are separate exclusions, so the cause of the water decides everything.
Why the standard policy says no
The ISO HO-3 (form HO 00 03, 2011 edition) lists the exclusion by name. Section I - Exclusion A.3 removes coverage for water that "overflows or is otherwise discharged from a sump, sump pump or related equipment," along with water that backs up through sewers or drains. The exclusion applies "regardless of any other cause or event contributing concurrently or in any sequence to the loss." If a lightning storm cuts power and the pump stops, the pump failure is not the point; the water that overflowed the sump is what the exclusion names.
The form also keeps sump equipment out of the one water coverage that would otherwise help. Where it covers an accidental discharge from plumbing, heating, air conditioning or a household appliance, it adds that these terms do "not include a sump, sump pump or related equipment or a roof drain, gutter, downspout or similar fixtures or equipment." A leak from a washing machine in the basement is a covered discharge. A flooded sump pit is not.
Power loss makes no difference. The form's power failure exclusion applies to failure of power or other utility service that "takes place off the 'residence premises.'" It has a carve-back for loss from a covered peril that follows the outage, but sump overflow is separately excluded, so the carve-back does not rescue the claim.
Four kinds of basement water
Basement claims go wrong when everyone uses one word, flooding, for four different problems. Insurers sort them by source. This table describes the standard HO-3 and typical add-ons; your policy and state endorsements control.
| Source of the water (hypothetical situations) | Standard HO-3 | What may cover it |
|---|---|---|
| A water heater tank splits or a washing machine hose bursts | Generally covered (accidental discharge from plumbing or an appliance) | Nothing extra needed |
| The sump pump fails, or the pit overflows in a storm | Excluded | Water backup and sump discharge or overflow endorsement |
| Sewage comes up the floor drain | Excluded | Same endorsement; see water backup and sewer backup coverage |
| Groundwater rises and seeps through the slab or walls | Excluded ("water below the surface of the ground") | Usually nothing; NFIP only if a flood caused it |
| Rain runs down the stairwell or through a window well | Excluded as surface water | Flood policy, if the event qualifies as a flood |
Only the first row works without an add-on. For the rest, the endorsement and a flood policy each cover a different slice, so a basement with any of these exposures is worth discussing with your agent in both contexts.
What the endorsement does with a sump pump
The water backup and sump discharge or overflow endorsement restores coverage for water that overflows or is discharged from a sump, sump pump or related equipment. The version filed by one AAA club insurer, for example, covers overflow that results from a sump pump's mechanical breakdown, but says the coverage "does not apply to direct physical loss of the sump pump, or related equipment, which is caused by breakdown." That is the common structure: the water damage to the basement is covered up to the endorsement's limit, and the pump itself is not. Limits are modest. In the North Carolina version of the ISO endorsement, a 2010 Rate Bureau circular described a basic limit of $5,000 with options of $10,000, $15,000 or $25,000. Each insurer chooses its own options, deductible and wording, including whether a pump that stops during a power outage is covered and whether negligence defeats the claim.
For a basement with a finished family room, laundry and bathroom, a $5,000 cap can be used up by flooring and drywall alone. water backup and sewer backup coverage walks through limit choices.
What a flood policy does and doesn't do
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. So an NFIP policy responds to a basement full of water when a covered flood caused the pump to be overwhelmed. It does not respond when your pump quits on a quiet night and the street is dry.
Even in a covered flood, the NFIP limits what it pays below the lowest elevated floor or in a basement. Sump pumps themselves are on the list of building items it covers in a basement, along with furnaces, water heaters and washers and dryers, but finished basement walls and most belongings are not (44 CFR Part 61, Appendix A(1)%20to%20Part%2061)). See what flood insurance covers in a basement and NFIP flood insurance explained. A flood policy also has a the 30-day flood insurance waiting period of 30 days in most cases, which does not help when rain is already in the forecast.
Groundwater and seepage
Water that rises through the slab or weeps through a foundation wall after wet weather is a groundwater problem. The HO-3 excludes "water below the surface of the ground, including water which exerts pressure on, or seeps, leaks or flows through a building, sidewalk, driveway, patio, foundation, swimming pool or other structure." It reads the same whether the soil is saturated by a storm or a high water table. Insurers generally treat this as a property-condition problem to fix with drainage, grading and waterproofing, not a sudden loss. Foundation cracks that let that water in raise a related question, covered in foundation cracks and settling: what's covered.
A worked example (hypothetical)
Say a thunderstorm knocks out power at 2 a.m. The sump pump stops, the pit fills and four inches of water spreads across a finished basement. Cleanup, flooring, drywall and the carpet in the family room total $22,000. You have a $1,000 deductible.
- No endorsement and no flood policy: the policy pays nothing for the water. You pay $22,000.
- A $10,000 water backup endorsement with a $500 deductible: the policy pays up to the limit, about $9,500 after the deductible, and you absorb the rest.
- A flood policy, if the storm created a qualifying flood: the NFIP could pay for covered basement items subject to its list, but not for finished walls, carpeting or most contents.
- The pump itself: your cost, unless you have equipment breakdown coverage: what it pays and who needs it and the failure qualifies.
The numbers are invented for illustration, but the structure is real: the answer depends on what is attached to your policy, not on the damage.
Mold and the cleanup that follows
Basement water that sits for more than a day or two grows mold, and mold has its own limits. The HO-3 excludes mold, fungus and wet rot except when it is hidden inside walls, ceilings or floors and results from a covered discharge from plumbing or an appliance. Mold that follows an excluded sump or groundwater event is not covered by that exception, and endorsements often cap mold at a small amount even when the water is covered. See does homeowners insurance cover mold?. Dry the space fast and keep photographs of the moisture readings.
A pump readiness checklist
FEMA's urban flooding guidance for Cook County, Illinois homeowners (November 2024, revised May 2025) notes that sump pumps "are not designed to handle large amounts of water, nor will they work when electricity is off," and that keeping one running through an outage requires battery storage or a generator. It also lists the questions a homeowner should ask: does the pump have battery backup, is there an alarm to warn when the water level rises above the sump, and is the pump maintained annually? Using that as a base:
- Test it every year, and before the wet season, by pouring water into the pit and watching the pump start and discharge.
- Add a battery backup or a water-powered backup, and a high-water alarm.
- Check where the discharge goes. The outlet should carry water well away from the house and not back toward the foundation.
- Know the age. A pump near the end of its life is a risk even if it works today.
- Disconnect downspouts from the sewer drain and point them away from the house.
- Keep the pit clear of debris and check the float moves freely.
- Document the setup: photographs of the pit, installation receipts, the maintenance history. If a loss happens, that record shows you took care.
Whether a pump alarm or water sensor earns a credit depends on the insurer; see water leak sensors and shutoff valves: discounts and value.
Key takeaways
- The standard HO-3 excludes sump pump overflow and discharge, groundwater seepage and surface water, however the pump fails.
- Only the water backup and sump discharge or overflow endorsement restores sump coverage, usually as a sublimit and usually without paying for the pump itself.
- An NFIP policy pays for a basement only when a qualifying flood is the cause, and then only for the items it lists.
- Plumbing and appliance leaks in the basement remain covered; the source of the water is what matters.
- Test the pump annually, add battery backup and an alarm, and check your declarations page for the endorsement before the next storm.