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Quick answer
What does the Water saving impact calculate?
How much water does a lower-flow habit save over time? This calculator uses old fixture flow, new fixture flow, minutes per use, uses per day, and days to estimate water avoided over time immediately in your browser.
With the values currently entered, the result is 11,571 gal — water saved. It also shows cubic metres saved, and saving per use.
How to use the Water saving impact
- Replace the example values with your own numbers.
- Review the result and supporting figures as they update automatically.
- Check the formula and assumptions before using the estimate for a decision.
Inputs used
- Old fixture flow — entered in L/min
- New fixture flow — entered in L/min
- Minutes per use — entered in minutes
- Uses per day — entered in uses
- Days — entered in days
Water saving impact formula
(Old flow − new flow) × minutes × daily uses × days
Assumptions
- Use duration and frequency do not increase.
- Measured fixture flow is more reliable than rated flow.
Practical guide
Water saving impact example and edge cases
How much water does a lower-flow habit save over time? Let's use a concrete example, then look at the assumptions that can move the answer.
Example: A practical water saving impact scenario
For this example, use old fixture flow of 12 L/min, new fixture flow of 7 L/min, minutes per use of 6 minutes, uses per day of 4 uses, and days of 365 days. These are starting values, so replace them with numbers that match your situation.
- Old fixture flow
- 12 L/min
- New fixture flow
- 7 L/min
- Minutes per use
- 6 minutes
- Uses per day
- 4 uses
- Days
- 365 days
Calculated result11,571 galwater saved
Start with water saved. Then check cubic metres saved, and saving per use to understand what sits behind the main result.
Example results use the default display profile. The calculator above follows your selected country and units.
How to read the result
- Read the main result first. The supporting figures for cubic metres saved, and saving per use explain how the estimate is built.
- The method is (Old flow − new flow) × minutes × daily uses × days. Keep the units consistent and use values from the same time period.
Edge cases worth checking
When old fixture flow is unusual
Use duration and frequency do not increase. Double-check this input before relying on the result.
When days is uncertain
Measured fixture flow is more reliable than rated flow. Run a lower and higher value to see a useful range.
What changes the result most
Old fixture flow
Measure old fixture flow with the same unit shown beside the input. Convert first if your source uses another unit.
New fixture flow
Measure new fixture flow with the same unit shown beside the input. Convert first if your source uses another unit.
Minutes per use
Keep minutes per use on the same time basis as the other inputs. Monthly and annual values are easy to mix up.
Try a different scenario
Small changes show whether the answer is stable or sensitive.
Old fixture flow: 10% lower
11 L/min9,257 galwater saved
Old fixture flow: 10% higher
13 L/min13,885 galwater saved
New fixture flow: 10% higher
8 L/min9,257 galwater saved
Common mistakes
Check old fixture flow
Use duration and frequency do not increase. Make sure this matches the number you enter.
Keep days consistent
Measured fixture flow is more reliable than rated flow. Use the same units and time period throughout the calculation.
Do not rely on one water saving impact scenario
Run a cautious case and an optimistic case. The range is often more useful than one exact-looking number.
Use this result well
How much water does a lower-flow habit save over time?
Impact factors vary by source, location, technology, and reporting method.