Track Nonpotable Storm Capture and Overflow into One Initially Empty Barrel — Free
A full barrel cannot collect the next shower just because its brochure capacity looks generous. Carry remaining headroom from storm to storm and distinguish potential runoff, captured water and spill under a clearly stated no-draw-off scenario.
The proof surface
Emergency-water headroom tools inventory potable supplies. This register models nonpotable roof runoff into a single initially empty container, updating cumulative storage and overflow. It does not recommend drinking roof water or size structural drainage.
InputStorm code | rainfall mm | contributing roof m² | modeled runoff fraction; usable barrel capacity (liters)
Rare deviceEmergency-water headroom tools inventory potable supplies. This register models nonpotable roof runoff into a single initially empty container, updating cumulative storage and overflow. It does not recommend drinking roof water or size structural drainage.
Output artifactCumulative modeled spill with no draw-off with row-by-row context
Cost$0 local calculation · no card, paid key, subscription or signup · proposed filing price is not for sale
Sample, not your facts: Illustrative inputs: October squall | 8 | 30 | 0.8; Next shower | 4 | 30 | 0.8. Usable barrel capacity (liters) = 180. Cumulative modeled spill with no draw-off: 108 L modeled overflow. All records are invented.
Before using the storm-capture register
One millimeter of rainfall over one square meter corresponds geometrically to one liter before collection losses. Multiply that by an explicitly supplied runoff fraction from zero through one. Use contributing horizontal collection area under your chosen verified convention, not sloping roof surface area without checking its relationship to rainfall. Rows are storms in chronological order. The barrel begins empty, there is no draw-off, evaporation, leak, first-flush deduction or connection limit between rows, and usable capacity is the volume available to this model rather than necessarily the advertised container size. Water is treated as nonpotable. The calculation cannot determine contamination, mosquito protection, foundation drainage or whether a collection installation is permitted.
Why the flat version breaks
Restarting capacity for every storm
The same barrel does not become empty when a new row begins. The register carries captured water forward, which is why a second storm can entirely spill. If real draw-off occurred, the assumed model must be changed openly rather than letting each row reuse full capacity.
Mixing roof surface and contributing collection area
Rainfall depth applies to a specified projected collection area. A larger sloping surface figure may overstate collection if used without reconciling its convention. Verify the area feeding the downspout and keep its source; the tool cannot map roof drainage from a house description.
Calling captured liters potable storage
Roof runoff may contain contaminants, and this model assesses volume only. No treatment, testing or hygiene process is represented. Keep the nonpotable label with copied results, and use qualified advice for water quality or drainage decisions rather than treating captured capacity as emergency drinking water.
How to work the storm-capture register
Confirm area, capacity and loss convention
Identify the roof area actually contributing to the barrel and a suitable runoff fraction for the scenario. Record the basis privately rather than presenting a guessed fraction as measured efficiency. Obtain usable capacity from the installation's reviewed setup. Structural, drainage and potable-water questions belong with qualified professionals, not this volume model.
Enter sequential storms without hidden draw-off
Use non-negative rainfall millimeters, positive contributing area and a fraction between zero and one. Put storms in the order observed or planned. If the barrel was emptied between storms, this no-draw-off sequence is not appropriate; create separately labeled runs with an explicit new initially-empty boundary instead of silently resetting storage within a row.
Allocate each inflow to remaining headroom
Potential runoff is rainfall × area × fraction in liters. Captured volume is the smaller of that inflow and remaining capacity. Overflow is inflow minus captured volume. Reduce headroom by captured volume before processing the next row. The register keeps all three quantities so cumulative spill cannot be confused with total rainfall or available drinking supply.
Check the installation rather than relying on modeled spill
Compare source measurements and actual barrel behavior if planning collection use. Ask a qualified installer about overflow routing, local requirements and safe maintenance. The app's spill number is not a drainage-design recommendation, and water quality must be assessed independently; do not use this output as a reason to drink untreated roof runoff.
What the storm-capture register separates
Question
Before
Inspect this instead
Restarting capacity for every storm
The same barrel does not become empty when a new row begins. The register carries captured water forward, which is why a second storm can entirely spill. If real draw-off occurred, the assumed model must be changed openly rather than letting each row reuse full capacity.
Enter sequential storms without hidden draw-off
Mixing roof surface and contributing collection area
Rainfall depth applies to a specified projected collection area. A larger sloping surface figure may overstate collection if used without reconciling its convention. Verify the area feeding the downspout and keep its source; the tool cannot map roof drainage from a house description.
Allocate each inflow to remaining headroom
Calling captured liters potable storage
Roof runoff may contain contaminants, and this model assesses volume only. No treatment, testing or hygiene process is represented. Keep the nonpotable label with copied results, and use qualified advice for water quality or drainage decisions rather than treating captured capacity as emergency drinking water.
Check the installation rather than relying on modeled spill
This storm-capture register replaces a manual count or calculation, not source verification or the responsible person’s review.
Run it on the samples, right here
FIRST-LOAD
HYPOTHESIS / PROTOTYPE — checkout unavailable. Calculation is local. A draft is saved automatically in this browser profile when storage is available; Reset to sample clears it. Optional Pro history stores only five summaries and has its own deletion control. State links encode your inputs and can remain in browser history, clipboard or recipients’ records; share only non-sensitive rows. Optional external AI formatting leaves this device. The required site analytics beacon reports page activity; shared URLs contain encoded inputs. Do not treat an encoded URL as private. The calculator has no input-collection endpoint.
Nonpotable collection-volume scenario only, not water-quality, drainage-design or installation advice. Do not drink untreated roof runoff; ask a qualified installer about overflow routing, maintenance and local collection requirements.
Data note: The storm-capture register processes Storm code | rainfall mm | contributing roof m² | modeled runoff fraction locally. Starter/sample selection and Run compute in this tab; no input is sent by the calculator. A local draft may be saved; explicit state-link sharing or optional external AI formatting can disclose inputs. Use non-sensitive labels.
Go deeper: the companion app files the same reading as a bound register page
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the storm-capture register reading, and holds your drafts on this device — one complete free app run; the proposed $4 one-time filing layer is not for sale.
The storm-capture register answer stays complete for free. The proposed $4 one-time filing layer adds row CSV, print and five local reading summaries, not hidden answers. Checkout is unavailable; the article demo remains unlimited.
Nonpotable collection-volume scenario only, not water-quality, drainage-design or installation advice. Do not drink untreated roof runoff; ask a qualified installer about overflow routing, maintenance and local collection requirements.
What this is built on
Method: Potential runoff is rainfall × area × fraction in liters. Captured volume is the smaller of that inflow and remaining capacity. Overflow is inflow minus captured volume. Reduce headroom by captured volume before processing the next row. The register keeps all three quantities so cumulative spill cannot be confused with total rainfall or available drinking supply.
All sample records, dates, quantities and labels are invented. No outside policy, contract, rate, clock offset, measurement or accessibility standard is represented as verified.
Google’s official pricing documentation, fetched 2026-10-01, says AI Studio is free in available regions. Optional formatting may require a Google account; manual local entry requires none. Limits can change and free-tier content may be used to improve products. Do not send private records.
Before: each shower seemed to reuse the whole barrel. After: sequential headroom separates potential runoff, captured volume and overflow.
Three worked readings, with different inputs
Sample A — typical inputs
October squall | 8 | 30 | 0.8
Next shower | 4 | 30 | 0.8
Eight millimeters over thirty square meters gives 240 liters before the 0.8 runoff factor, or 192 modeled liters. The empty 180-liter barrel captures 180 and spills twelve. The next shower contributes ninety-six liters, but with no draw-off the barrel is full and all ninety-six spill. Total overflow is 108 liters; summing each storm as though the barrel restarted empty would understate the second spill.
The first storm contributes forty-eight liters and the second seventy-two. Their cumulative 120 liters fit within the usable capacity, leaving sixty liters of modeled headroom and no spill. This does not verify actual collection efficiency: gutter losses, first-flush diversion and leaks can differ from the supplied runoff fraction.
The model gives 7.5×30×0.8 = 180 liters, exactly the supplied usable capacity. Overflow is zero and remaining headroom is zero. The equality is a geometry-and-factor boundary, not a guarantee that a real barrel will stop precisely at that volume or that collected roof water is potable.
Optional AI formatting, never the calculation
Manual entry completes this storm-capture register for free without signup. If available to you, the free AI Studio interface linked in the sources may format fictional or non-sensitive notes; external access may require an account. No API key or AI call is built into this tool. Free-tier content may be used to improve products. Review each cell and transcribe it to the labeled row schema; do not paste the JSON object into the row box.
Format only these fictional or non-sensitive notes for a storm-capture register. Return strict JSON shaped as {"rows": [{"label": "string", "cells": ["string", "string", "string"]}], "setting": "string"}. The columns are Storm code | rainfall mm | contributing roof m² | modeled runoff fraction; the setting is Usable barrel capacity (liters). Keep all supplied strings and quantities exactly; do not calculate, infer missing entries, invent dates or add advice. If any required value is missing, return an empty rows array and ask me for it separately. I will verify every cell against my source and manually transcribe rows using vertical bars before running the local calculator.
An AI response is not executed, fetched or trusted as a result. Missing values remain questions; the strict local parser checks the rows you actually enter.