Toilet Water Savings Calculator
Gallons and dollars saved swapping old toilets for 1.28 gpf.
What it does
Toilets drink nearly 30% of indoor home water, so old tanks dominate the bill: swapping 3.5 gallons per flush for 1.28 saves 2.22 gallons every flush, which compounds across every person every day.
The tool above takes old flush volume with daily flushes and water price. It returns daily and yearly gallons with dollars beside them. The default 3.5 gpf at 20 flushes saves 44.4 gal a day, 16,206 gal a year, $243.09.
Volumes match EPA WaterSense with Alliance efficiency data beside them: 1.28 gpf certified against the 1.6 federal standard, old tanks to 6 or 7 gpf, and 6 flushes a day saving about 13 gallons daily. EPA family averages land near 13,000 gallons and over $170 a year.
Performance fears date to early low flow models. Modern certified bowls clear waste in one flush under independent testing, and dual flush modes shave liquid waste further.
How to use
- Read old gpf inside the tank or lid stamp.
- Count whole household flushes per day.
- Type water price with sewer share.
- Read daily first, yearly beside it.
- Compare yearly against 13,000 EPA anchor.
- Claim utility rebates before buying.
Formula
- 1.28
- WaterSense gallons per flush ceiling.
- flushes
- Whole household flushes per day.
- price
- Water plus sewer dollars per gallon.
Dual flush reduced modes save more on liquid waste; this page prices full flush replacement only. Leaking flappers waste past every number here.
Worked example
Example: 3.5 gpf, 20 flushes
Defaults: 3.5 gpf old, 20 flushes, $0.015/gal.
- Per flush: 3.5 minus 1.28 = 2.22 gal.
- Daily: 2.22 x 20 = 44.4 gal.
- Yearly: 44.4 x 365 = 16,206 gal.
- Money: 16,206 x $0.015 = $243.09.
- EPA check: average family near 13,000 gal.
- Tool shows 44.4 gal/day, 16,206 gal/year, $243.09/year.
Reference table
| Case | Per flush saved | Yearly at shown flushes |
|---|---|---|
| 3.5 to 1.28, 6/day | 2.22 gal | 13.3 gal/day, 4,862 gal/yr |
| 3.5 to 1.28, 20/day | 2.22 gal | 44.4 gal/day, 16,206 gal/yr |
| 6 to 1.28, 6/day | 4.72 gal | 28.3 gal/day, 10,337 gal/yr |
| EPA family average | 20 to 60% cut | 13,000 gal, $170+/yr |
| Federal standard | 1.6 gpf | 20% above WaterSense |
| Toilets share indoor | Near 30% | Top home use |
Limits
- Full flush math; dual modes save more.
- Behavior fixed; habits shift results.
- Rebates and install costs excluded.
- Leaks add waste outside these lines.
Common mistakes
- Counting per toilet instead of household.
- Pricing water without sewer share.
- Comparing against 1.6 instead of old gpf.
- Skipping flapper leaks that dwarf savings.
- Buying before checking rebates.
Try it yourself
Quick checks. Answers sit tucked under each question.
3.5 gpf at 6 flushes?
13.3 gal/day, 4,862 gal/year.
6 gpf at 6 flushes?
28.3 gal/day, 10,337 gal/year.
Already 1.28?
Rejected: old volume must exceed 1.28 gpf.
Questions
Default savings?
44.4 gal a day, 16,206 a year, $243.09.
WaterSense line?
1.28 gpf max, 20% under the 1.6 federal standard.
Old tanks?
3.5 standard with many at 5 to 7 gpf.
EPA family anchor?
Near 13,000 gallons and over $170 a year.
Dual flush?
Reduced mode saves more on liquids; this prices full flush.
Faucet page versus this?
That prices drip waste; this prices flush replacement.