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Problem Solving Guide
How Much Does a Running Toilet Cost Per Month
A constantly running toilet can quietly inflate your water bill. This guide calculates the real monthly cost based on water rates, leak severity, and toilet type, and shows you how to stop the waste.
Why Trust Best Flushing Toilets
- Flushing power and MaP flush-test scores
- Water efficiency (GPF and EPA WaterSense)
- Aggregated owner reviews
- Clog resistance and trapway design
- Brand reliability and warranty
Research updated June 2026.
Quick Answer
A running toilet can cost between $6 and $60 per month, depending on the severity of the leak and your local water rates. A slow leak (1 gallon per hour) adds roughly $3, $8 per month, while a fast leak (6+ gallons per hour) can exceed $50. Most leaks are caused by a worn flapper or stuck fill valve and are cheap to fix.
How Do You Calculate the Cost of a Running Toilet?
To calculate the cost, measure the leak rate in gallons per hour, multiply by hours per month, then multiply by your water rate per gallon. A typical residential water rate in the U.S. is about $0.005 per gallon, though rates vary by region.
The formula is simple: Leak rate (GPH) x Hours per month (730) x Water rate ($/gallon) = Monthly cost. For example, a toilet losing 3 gallons per hour at $0.005/gal costs 3 x 730 x 0.005 = $10.95 per month. If your water rate is higher (e.g., $0.008/gal in some cities), that same leak jumps to $17.52 per month.
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To measure your toilet’s leak rate, place a few drops of food coloring in the tank. Wait 15 minutes without flushing. If color appears in the bowl, you have a leak. Then, mark the water level in the tank, turn off the water, and measure how much water is lost over an hour using a measuring cup or by refilling to the mark.
Expert Take
Many homeowners underestimate running toilet costs because they only notice the sound. A silent leak can waste 200+ gallons per day without any audible cue. Always check with dye tablets, not just your ears.
What Is the Average Monthly Cost of a Running Toilet by Leak Severity?
A slow leak (0.5, 1 GPH) costs $2, $8 per month. A moderate leak (3, 5 GPH) costs $12, $30 per month. A severe leak (6, 10+ GPH) costs $30, $60+ per month. The national average for a moderate leak is about $18 per month.
| Leak Severity | Gallons Per Hour | Monthly Waste (gal) | Avg. Monthly Cost |
|---|---|---|---|
| Slow (drip) | 0.5, 1 | 365, 730 | $2, $8 |
| Moderate (trickle) | 3, 5 | 2,190, 3,650 | $12, $30 |
| Severe (steady flow) | 6, 10 | 4,380, 7,300 | $30, $60+ |
These estimates assume a water rate of $0.005 per gallon. In cities like Los Angeles, San Francisco, or New York, rates can be double or triple, pushing a severe leak past $100 per month. Conversely, in rural areas with well water, the cost may be limited to electricity for pumping.
Aggregated owner reviews on forums like Terry Love and Reddit frequently report surprise bills of $50, $80 from a single running toilet. The EPA estimates that household leaks waste nearly 1 trillion gallons annually in the U.S., with toilets being the most common culprit.
Which Toilet Models Are Most Prone to Running Leaks?
No toilet brand is immune, but older models with standard 3-inch flappers and gravity-feed designs tend to have more flapper failures. Pressure-assist toilets rarely run, but their fill valves can stick. WaterSense-certified models with high-quality components, like the TOTO Drake II, have fewer reported leak issues.
Based on aggregated owner reviews and manufacturer service data, here are common models and their typical leak points:
| Model | MaP Score | GPF | Flush Type | Trapway | Height | Best For | Check Price |
|---|---|---|---|---|---|---|---|
| TOTO Drake II CST454CEFG | 1000g | 1.28 | Gravity (Tornado) | 2-1/8" | 17" | Reliability | Check price |
| Kohler Highline K-3609 | 800g | 1.28 | Gravity | 2" | 17" | Value | Check price |
| American Standard Champion 4 | 1000g | 1.6 | Gravity | 2-3/8" | 16.5" | Clog resistance | Check price |
| Woodbridge T-0001 | 1000g | 1.28 | Dual flush | 2-1/8" | 17" | Budget dual flush | Check price |
| Gerber Viper 21-528 | 800g | 1.28 | Gravity | 2" | 17" | Commercial use | Check price |
Older toilets (pre-1994) use 3.5, 5 GPF and have larger flapper seats that warp over time. Modern WaterSense models use 1.28 GPF and have improved gasket materials. However, even a new toilet can run if the fill valve is misadjusted or the chain is too tight.
Expert Take
If you own a pressure-assist toilet like the Kohler Wellworth Pressure Lite, a running issue is almost always the fill valve diaphragm, not the flapper. These are less common but more expensive to repair. Gravity toilets are simpler and cheaper to fix.
How Can You Fix a Running Toilet Yourself?
Most running toilets are fixed by replacing the flapper, adjusting the fill valve height, or cleaning the fill valve seat. These repairs cost $5, $20 in parts and take 15, 30 minutes. If the flush valve is cracked, replacement costs $20, $50.
Follow these steps to diagnose and fix a running toilet:
- Check the flapper: If it’s warped, cracked, or dirty, replace it with a universal flapper ($5, $10). Ensure the chain has 1/4 inch of slack.
- Adjust the fill valve: If water is overflowing into the overflow tube, turn the adjustment screw on top of the fill valve counterclockwise to lower the water level.
- Clean the fill valve: If the valve is hissing or not shutting off, remove the cap and rinse out debris. Soak in vinegar if mineral deposits are present.
- Replace the fill valve: If cleaning doesn’t work, install a new Fluidmaster 400A ($10, $15).
- Check the flush valve seal: If water leaks past the flapper even when new, the flush valve seat may be rough. Use a flush valve repair kit ($15, $20).
If you’re not comfortable with DIY, a plumber will charge $100, $200 for the service call. That’s often cheaper than letting a leak run for 3, 4 months.
Does a Running Toilet Waste More Water Than a Leaky Faucet?
Yes. A running toilet wastes far more water than a leaky faucet. A faucet dripping once per second wastes about 3 gallons per day. A toilet with a slow leak wastes 12, 24 gallons per day. A severe toilet leak can waste over 200 gallons per day.
To put it in perspective: a faucet drip at 10 drips per minute wastes about 1 gallon per day. That’s 30 gallons per month. A toilet with a visible trickle wastes 3, 5 gallons per hour, or 2,160, 3,600 gallons per month. That’s 72, 120 times more waste.
The EPA’s WaterSense program reports that easily fixable household leaks waste an average of 10,000 gallons per year per home. Toilets account for about 30% of that total. Fixing a running toilet is the single most impactful water-saving measure you can take.
Frequently Asked Questions
How much does a running toilet cost per month on average?
On average, a running toilet costs between $6 and $60 per month. The exact cost depends on the leak rate and your local water rates.
Can a running toilet cause a high water bill?
Yes. A running toilet is one of the most common causes of unexpectedly high water bills. A moderate leak can add $15, $30 per month.
How do I know if my toilet is running?
Listen for a hissing or trickling sound. You can also add food coloring to the tank; if color appears in the bowl within 15 minutes, you have a leak.
What is the most common cause of a running toilet?
A worn or misaligned flapper is the most common cause. The flapper degrades over time and no longer creates a watertight seal.
How much water does a running toilet waste per day?
A slow leak wastes 12, 24 gallons per day. A severe leak can waste 144, 240 gallons per day or more.
Is it cheaper to fix a running toilet or let it run?
It is always cheaper to fix it. A $10 flapper repair pays for itself in 1, 2 months of reduced water bills.
Does a running toilet waste more water in summer?
Water waste is the same year-round, but if you’re on tiered water rates, summer usage may push you into a higher rate bracket, increasing cost.
Can a running toilet cause sewer gas smells?
Yes. If the toilet runs constantly, the water in the trap can be replaced too quickly, allowing sewer gases to escape.
How long can a toilet run before it causes damage?
There’s no immediate damage, but prolonged running can wear out the fill valve and cause the tank to sweat, potentially damaging flooring.
Does a running toilet affect water pressure?
No. A running toilet does not affect water pressure in the rest of the house. It only wastes water.
Should I call a plumber for a running toilet?
If you can’t fix it with a new flapper or fill valve adjustment, call a plumber. The cost of a service call is less than 2, 3 months of a severe leak.
What is the best toilet to avoid running leaks?
Toilets with high-quality components like the TOTO Drake II or American Standard Champion 4 have fewer reported flapper issues. Look for models with a 5-year warranty on parts.
Can a running toilet be silent?
Yes. A silent leak occurs when water flows through the overflow tube without making noise. Dye testing is the only reliable way to detect it.
How much does it cost to replace a toilet fill valve?
A new fill valve costs $10, $15. If you hire a plumber, expect to pay $100, $200 total for parts and labor.
Sources
- EPA WaterSense, epa.gov/watersense
- MaP flush testing, map-testing.com
- Manufacturer published specifications
- American Water Works Association, awwa.org
- Terry Love Plumbing & Remodel DIY Forum
Our Verdict
A running toilet is a silent money waster that can cost $6, $60 per month depending on leak severity and local water rates. The fix is almost always cheap and easy: replace the flapper or adjust the fill valve. Don’t ignore the sound or the dye test. Fixing a running toilet is the fastest way to lower your water bill and conserve thousands of gallons annually.
How we rank & our data sources
We do not run physical lab tests. Rankings are built from published, verifiable data and real owner feedback, never paid placement.
- MaP (Maximum Performance) flush scores
- EPA WaterSense certification & GPF ratings
- Manufacturer specifications (trapway size, flush-valve, rough-in)
- Verified owner reviews from Amazon, Home Depot & Lowe’s
Researched by Marcus Bell · Last updated June 28, 2026 · Our review method
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