Water backup endorsement
Definition
A water backup endorsement adds limited coverage for water that backs up through sewers or drains or overflows from a sump pump, damage a standard homeowners policy excludes. Flood from outside is still excluded.
What it means
The standard ISO homeowners form (HO 00 03) excludes water or water-borne material that “backs up through sewers or drains” or overflows from a sump, sump pump or related equipment. That means a sewage backup in the basement is usually not covered unless you add coverage.
The ISO endorsement for this is HO 04 95, Limited Water Back-Up and Sump Discharge or Overflow Coverage. It covers direct physical loss from those sources up to a scheduled limit. ISO’s 2022 program adds HO 06 95 for broader limits. The endorsement does not cover flood or surface water, which needs a separate flood policy.
Why it matters to your claim
Without this endorsement, a sewer or sump backup can leave you paying for Category 3 cleanup yourself. With it, you are still capped at the endorsement limit, which may be far below the cost of a finished basement. Check your declarations page for the endorsement and its limit. If floodwater also entered from outside, ask how your insurer and any flood insurer will split the claim. Our page on sewer backup coverage explains the endorsement in detail.
Sources
- Homeowners 3 Special Form, HO 00 03 10 00 (ISO sample policy), Insurance Services Office, via Insurance Information Institute (form edition 10 00; accessed 2026-10-19)
- Limited Water Back-Up and Sump Discharge or Overflow Coverage, Form HO 04 95, InsuranceXDate (accessed 2026-10-19)
- 44 CFR Part 61, Insurance Coverage and Rates (Standard Flood Insurance Policy forms), Electronic Code of Federal Regulations (accessed 2026-10-19)
Updated October 19, 2026. Drafted with AI assistance and edited by Vincent Wallace. All glossary terms