Plumbing
Water saving fixture payback
Price supplied flow reduction and observed usage without selecting fixtures.
Your inputs
Complete the fields for your selected method. Zero means intentionally zero, not unknown. Currency selection labels amounts; it does not convert exchange rates.
How this calculation works
saved volume=(old-new flow)*minutes*uses; payback=cost/savings.
Measured flow and use assumptions; no fixture selection or code compliance. Does not include hot-water heating savings. Negative savings are retained.
What information do I need?
Use records for the same job, equipment or accounting period. Only the fields for your selected entry method are required. An unknown amount is not zero.
Input definitions and where to find them
- Existing measured fixture flow (US gal/min): Collected water volume ÷ collection time at current conditions.
- Proposed measured fixture flow (US gal/min): Measured or labeled rated proposed flow at comparable conditions.
- Minutes per use (minutes/use): Actual time from logs/calendar/statement, or an explicitly labeled future schedule. Keep the period in minutes per use consistent with all matching costs/outputs.
- Uses per year (uses/year): Use matching records or a clearly identified owner assumption for uses per year, in the displayed unit and the stated row/period scope.
- Combined water and sewer price (currency/1,000 US gal): Matching invoice, quote, statement, bookkeeping record or explicit budget amount for combined water and sewer price. Use the stated period and exclude amounts already counted in another field. Zero means intentionally excluded/not incurred, not unknown.
- Installed replacement cost (selected currency): Matching invoice, quote, statement, bookkeeping record or explicit budget amount for installed replacement cost. Use the stated period and exclude amounts already counted in another field. Zero means intentionally excluded/not incurred, not unknown.
Use the Where to find this value controls beside the inputs for available work-it-out helpers. Estimates remain your assumptions; a helper does not verify the source figures.
Worked example
Example amounts use US dollars (USD).
Example answer: Annual water volume saved is 20.00 m³/year for the illustrative inputs below.
Example inputs
- Existing measured fixture flow: 2.641720523581 US gal/min
- Proposed measured fixture flow: 1.585032314149 US gal/min
- Minutes per use: 5.00 minutes/use
- Uses per year: 1,000.00 uses/year
- Combined water and sewer price: 18.927058920000 currency/1,000 US gal
- Installed replacement cost: $200.00
- Annual water volume saved
- 20.00 m³/year
- Annual water and sewer savings
- $100.00
- Simple payback
- 2.00 years
These illustrative values are not recommended rates or industry averages. Replace every example input with your own figures.
Use the result well
Price supplied flow reduction and observed usage without selecting fixtures.
Keep inputs on the same scope and time basis. Calculations retain precision internally; displayed values generally round to two decimal places, with extra precision for very small values and whole-unit rounding where required. Economic comparisons describe your supplied assumptions and do not guarantee future results.
This tool provides business arithmetic. It does not approve engineering designs, establish legal or tax treatment, select equipment or certify safe operating conditions.