In short: a faucet dripping about once per second wastes roughly 5.7 gallons a day — about 2,080 gallons a year — which comes to only around $15.62 a year at a typical rate of $7.50 per 1,000 gallons. A running toilet or pipe leak can waste ten to a hundred times that much, so it's worth measuring your actual leak rather than assuming.
These are planning estimates from a measured or estimated leak rate and the rate you enter. Your water bill is the true measure — use it to sanity-check the result.
How the cost is calculated
Every leak is just a flow rate running continuously — 1,440 minutes a day, every day, whether or not anyone notices. The calculator converts whatever you measured into gallons per minute, multiplies by the minutes in a day, month or year, then multiplies by your water rate (and sewer rate, if you include it):
gallons wasted = leak rate (GPM) × 1,440 × days
cost = gallons wasted × ($/gallon)
A drip count is converted using the USGS estimate of about 15,140 drips per gallon. A timed catch converts the volume you collected into gallons per minute. A known flow rate is converted to gallons per minute directly.
Worked example. A faucet dripping once per second (60 drips a minute) works out to about 0.0040 gallons a minute, or 5.71 gallons a day — about 174 gallons a month and 2,083 gallons a year. At $7.50 per 1,000 gallons, that's roughly $0.043 a day, $1.30 a month, and $15.62 a year in water charges alone.
Drip rate to gallons and cost
Figures assume the same 15,140-drips-per-gallon estimate and a $7.50-per-1,000-gallon water rate used above. Enter your own drip count and rate in the calculator for an exact match.
| Drip rate | Gal / day | Gal / year | Cost / year |
|---|---|---|---|
| 15 drips/min (1 every 4s) | 1.43 | 521 | $3.91 |
| 30 drips/min (1 every 2s) | 2.85 | 1,042 | $7.81 |
| 60 drips/min (1/sec) | 5.71 | 2,083 | $15.62 |
| 90 drips/min | 8.56 | 3,124 | $23.43 |
| 120 drips/min (2/sec) | 11.41 | 4,166 | $31.24 |
Why the measurement method matters
A drip count is convenient but imprecise — drop size varies with the fixture and how worn the washer or flapper is, so the 15,140-drips-per-gallon figure is an average, not a universal constant. A timed catch (collecting the leak in a container for a fixed time) is far more accurate because it measures the actual volume, and it works for leaks a drip count can't capture, like a pipe joint or a valve that's weeping rather than dripping.
A known flow rate is the most direct option — useful when a plumber has already quoted a rate, or when a meter test (reading your meter with everything off) has told you how fast water is moving. Whichever method you use, the underlying math is identical: it's always rate × time × price.
Worked examples
Dripping faucet
$15.62/yr
60 drips/min (1/sec), $7.50 per 1,000 gal. About 5.7 gal/day, 2,083 gal/year.
Running toilet
~$246/yr
Timed catch: 8 fl oz in 60 seconds → 0.0625 GPM. About 90 gal/day, 32,850 gal/year at $7.50/1,000 gal.
Small pipe leak
$131.40/yr
Known flow rate: 2 gal/hour → 48 gal/day, 17,520 gal/year at $7.50/1,000 gal.
What else affects the real cost
Tiered billing. Many utilities charge more per gallon once you pass a threshold. This tool applies one flat rate, so if your usage is tiered, enter your highest-tier rate for a more realistic, conservative number.
Sewer charges. A lot of utilities bill sewer as a percentage of metered water use, even for water that never reaches the sewer — like an indoor leak that evaporates or an outdoor irrigation leak. Toggle the sewer field on if that applies to your bill.
Undetected leaks. A silent toilet flapper leak can run for months before anyone notices, which is why a sudden, unexplained jump in a water bill — or a meter that keeps moving with everything off — is worth investigating with the running toilet cost calculator or the timed catch method above.
Frequently asked questions
How much does a small drip actually cost per year?
A faucet dripping about once per second (60 drips a minute) wastes roughly 5.7 gallons a day, or about 2,080 gallons a year. At a typical rate of $7.50 per 1,000 gallons, that is only around $15.62 a year in water charges alone — the real cost usually comes from letting several small leaks run for years, or from a leak large enough to trip a higher billing tier.
How do I know if my toilet is running or leaking?
Add a few drops of food coloring to the tank and wait about ten minutes without flushing. If color shows up in the bowl, the flapper is leaking. You can then use the timed catch or known flow rate method here to estimate the cost.
How is this different from the dripping faucet or running toilet calculators?
The dripping faucet and running toilet tools are built around one fixture's typical measurement. This calculator accepts any measured leak rate — a drip count, a timed catch from any fixture or pipe, or a known flow rate — so it works for faucets, toilets, irrigation lines, and pipe leaks alike.
Should I include a sewer charge?
Include it if your utility bases your sewer charge on metered water use, which is common. Leave it off if the leaked water clearly does not reach the sewer, such as an outdoor irrigation line or hose bib leak, or if your utility bills sewer at a flat rate.
Does this account for tiered water rates?
No, this tool applies one flat rate to every gallon. If your utility uses tiered or block rates, enter the rate for the highest tier your usage reaches for a more conservative, realistic estimate.
Sources & references
- U.S. Geological Survey (USGS). Water Science School: How much water does a leaky faucet waste?
- U.S. Environmental Protection Agency (EPA). WaterSense: Fix a Leak Week facts and statistics.
- American Water Works Association (AWWA). Water audits and billing units (CCF, cubic meters).
Sarah Bennett, MS
Water Quality & Sustainability Specialist · Portland, Oregon
Environmental scientist (MS, Water Resources) with 9+ years in residential water quality, treatment, and usage efficiency, and 150+ completed assessments. Sarah writes and reviews the treatment, usage, and cost calculators on watercalculator.us. Read full bio
MS Environmental Science, Water Resources (2018) · BS Environmental Engineering (2016)