Exposure and redundancy
What a failure would cost you, using your numbers not ours
Every article about sump pumps eventually quotes a figure for what a flooded basement costs. We are not going to, and it is worth explaining why rather than just leaving a hole. Those figures are aggregates over housing stock, finishes, water depth, and insurance terms that have nothing to do with your basement. Printing one next to your address gives a stranger's average the authority of a personal estimate, and people make real decisions on that.
What can be done honestly is arithmetic on your numbers. You know what is down there and roughly what it would cost to put back. You know your deductible and whether the policy covers this at all. From those, plus how long the power has actually gone out at this address, the tool can show a planning tier for comparison — and every dollar in it came from you.
Your exposure, from your own valuations
Site-authored planning tier — not a recommendation
Battery backup plus a second primary pump staged higher in the pit
A screening result based on $39,000 you entered as your exposure and a 14-hour longest outage.
Why the screening rule chose that tier
- You absorb $39,000 of the loss yourself. At that number the failure worth defending against is not just the power going out — it is the pump itself failing while the power is on, which a battery backup on the same pit does not cover unless it is a separate pump.
Biggest swing factor Whether your policy actually responds. The same physical flood is a deductible or a total loss depending on an endorsement you either bought or did not, and that single fact moves the out-of-pocket number more than any hardware choice on this site.
- You indicated this peril is not covered. Confirm the applicable coverage, exclusions, deductible and sublimit with your insurer before comparing that exposure with any backup option.
- Your furnace, water heater, or panel sits in the water line. Those fail at a few inches, long before the finishes do, and they take the heat and hot water with them on the same night.
What this figure is not
- Any national average cost of basement flooding. We do not hold one, on purpose. Every dollar on this page is a figure you supplied about your own house.
- Mould remediation and the time it takes, which depends on how long the water sat and on materials we cannot see.
- Loss of use, temporary accommodation, and the hours you personally spend on the cleanup.
- Any change in your premium after a claim, which only your insurer can tell you.
- The probability that a flood happens at all. This is severity, not risk — we do not know your odds and we will not pretend to.
This is severity, not risk
The number above is what a failure would cost, not how likely one is. We do not know your odds and we are not going to model them — that would require knowing your water table, your drainage, the age of your pump, and the reliability of your utility, and any figure we produced would be a guess wearing a percentage sign.
Severity is still useful as one side of a comparison, but it does not set a rational equipment budget by itself. This tool does not estimate failure probability or expected loss, so compare the $39,000 exposure you entered with actual option costs and failure coverage rather than treating the screening tier as a purchase instruction.
The one place probability genuinely enters is outage history, which you actually have data on. A house that loses power three times a year for hours at a time is not making a hypothetical argument for a battery backup; it is describing a recurring operating condition.
The question worth asking your insurer this week
Coverage for sump failure and water backup varies by policy, endorsement, exclusion and cause. That policy-specific answer can move the number above further than any hardware assumption on this page, because it determines whether the loss is covered and which deductible or sublimit applies.
Confirm in writing whether the event you are planning for is covered, which deductible applies, and whether the coverage has a sublimit. The calculator treats your yes-or-no entry and deductible as a simplified scenario; it cannot interpret policy language or model partial coverage.
We will not publish a dollar figure for "what a flooded basement costs" and attach it to your house. The number depends on your finishes, your contents, your insurance, and your deductible. You supply the values; the tool does the arithmetic and shows the exposure.
The four depths, and what each one actually defends against
| Depth | Defends against | Does not defend against |
|---|---|---|
| High-water alarm only | Not noticing. Turns a flood into a wet floor when someone is home. | Anything at all when the house is empty. |
| Battery backup pump | The power going out during a storm. | A primary pump that fails while the power is on, unless the backup is a genuinely separate pump. |
| Battery plus a second primary | Pump failure, switch failure, and power failure — three separate causes. | A blocked or frozen shared discharge line, which takes both pumps at once. |
| Generator feeding the primary | Multi-day outages that no battery covers. | Anything that happens while nobody is home to start it, unless it is an automatic standby unit. |
Notice the last column on the third row. Redundant pumps sharing one discharge line are not fully redundant, and that is the failure people are most surprised by. If the exposure justifies two pumps, it usually justifies asking whether they can have separate discharge routes as well.
Related tools
- Backup runtime — whether the battery you are considering covers the 14-hour outage above.
- Install scope — what adding that depth puts on the quote.
- Sizing calculator — a correctly sized primary is the cheapest reliability you can buy.