In short: a running toilet typically wastes anywhere from about 30 to 200+ gallons a day. At a common rate of $6.50 per 1,000 gallons, that's roughly $6 to $40 a month — or well over $200 a year for a bad leak — for water that never gets used. Enter your own leak rate and rates above for a figure specific to you.
This is a planning estimate from the leak rate and rates you enter, not a bill. Local rates, tiers and sewer billing vary — check a recent bill to fine-tune the inputs.
How the cost is calculated
A running toilet leaks continuously (or for however many hours a day it's active), so the water lost is just the leak rate multiplied by the time it runs. That volume, in thousands of gallons, is then multiplied by your water rate — and your sewer rate, if your utility bills sewer service based on metered water use:
gallons wasted = leak rate (GPM) × 60 × hours/day
cost/day = (gallons wasted ÷ 1,000) × (water rate + sewer rate)
Monthly and yearly costs scale the daily figure by 30.44 days and 365 days.
Worked example. A moderate leak of 0.06 GPM running all day wastes 0.06 × 60 × 24 = 86.4 gallons a day. At $6.50 per 1,000 gallons with no separate sewer charge, that's 86.4 ÷ 1,000 × $6.50 = $0.56 a day, or about $17.09 a month and $204.98 a year — all from a leak most people never notice.
Typical leak rates and what they cost
These figures assume the leak runs 24 hours a day at $6.50 per 1,000 gallons, with no sewer charge — adjust the calculator above for your own rates and hours.
| Leak type | Rate | Gal / day | Cost / month | Cost / year |
|---|---|---|---|---|
| Silent leak (worn flapper) | 0.02 GPM | 28.8 | $5.70 | $68.33 |
| Moderate leak | 0.06 GPM | 86.4 | $17.09 | $204.98 |
| Running continuously | 0.14 GPM | 201.6 | $39.88 | $478.30 |
Source: EPA WaterSense estimates a running toilet can waste up to 200 gallons a day, which matches the "running continuously" row above.
A few real scenarios
Barely-there flapper leak
$5.70 / mo
0.02 GPM, 24 hrs/day, $6.50 per 1,000 gal — easy to miss without a dye test, but it adds up to over $68 a year.
Typical "phantom flush" leak
$17.09 / mo
0.06 GPM, 24 hrs/day, $6.50 per 1,000 gal — the fill valve you occasionally hear kick on by itself.
Stuck fill valve, water and sewer billed
$52.16 / mo
0.14 GPM, 24 hrs/day, $6.50 water + $2.00 sewer per 1,000 gal — audible running, billed for both water and sewer.
What else affects the number
Tiered rates. Many utilities charge more per gallon once you pass a monthly threshold. This calculator applies one rate to all the wasted water, which is accurate for most homes; if a leak pushes you into a higher tier, use that marginal rate for a more conservative estimate.
Sewer billing. Many utilities bill sewer service as a multiple of metered water use, so a running toilet can quietly inflate both halves of the bill. Check a recent statement for a separate sewer or wastewater rate.
How long it's been running. The yearly figure assumes the leak continues uncorrected for a full year. If you just noticed it, the cost so far is smaller — but the monthly and yearly figures are exactly what you'll keep paying, and exactly what you'll save, once it's fixed. For the wasted water itself, see the toilet water usage calculator.
Frequently asked questions
How much water does a running toilet waste?
It depends on the leak. A silent leak (a worn flapper that lets a little water past) can waste around 30 gallons a day. A toilet that runs continuously because the fill valve will not shut off can waste 200 gallons a day or more, according to EPA WaterSense. Most running toilets fall somewhere in between.
How do I know if my toilet is running?
Listen for a faint hiss or trickle from the tank between flushes. If you cannot hear anything, put a few drops of food coloring in the tank and wait 10 minutes without flushing. If color shows up in the bowl, the flapper is leaking. A fill valve that keeps cycling on its own is a clearer sign of a continuous leak.
Why does the calculator ask for hours per day?
Most running-toilet leaks are effectively continuous, so 24 hours is a reasonable default. But if the leak only shows up after certain flushes or you have already partly fixed it, lowering the hours gives a more accurate estimate instead of assuming it runs all day.
Should I include a sewer rate?
Include it if your utility bills sewer service based on metered water use, which many do. Check a recent bill for a separate sewer or wastewater line item and its rate per 1,000 gallons. If your sewer charge is a flat fee unrelated to usage, leave the sewer rate at zero.
Does my water rate change how much I'm losing?
Yes. This calculator applies one rate to all the wasted water, which matches how most residential tariffs work for a small amount of extra use. If your utility bills in increasing tiers and the leak pushes you into a higher tier, use that higher marginal rate for a more conservative estimate.
How much could I save by fixing it?
The monthly and yearly figures above are exactly what you would save by fixing the leak, since a repaired toilet uses no water between flushes. A new flapper or fill valve typically costs $10 to $25 and pays for itself in weeks for a moderate or severe leak.
Sources & references
- U.S. Environmental Protection Agency (EPA). WaterSense: Fix a Leak Week, Statistics and Facts.
- U.S. Geological Survey (USGS). Water Q&A: Water leaks at home.
There is no single national tariff for water and sewer service — rates, tiers and fixed charges vary by utility. This tool uses the rates you enter; check a recent bill for your own numbers.
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)