Water leak cost calculator

Measure the water loss. Apply your own bill rates.

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Quick answer

Measure the leak, then apply your water and sewer rates below. Moen’s 920-004 alerts at one spot, a plumber-fitted Flo 900-001 can shut the main, and Zircon’s Leak Alert is a plain local alarm.

Moen Flo 920-004 moisture detector$54.72 at AmazonPrice as of Oct 24, 2026, 5:30 AM EDT

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Best for a remote sensing disc

Moen Flo 920-004 moisture detector

$54.72 at Amazon

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Price as of Oct 24, 2026, 5:30 AM EDT

Best for main-line shutoff

Moen Flo 900-001 automatic shutoff

$559.00 at Amazon

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Price as of Oct 24, 2026, 5:30 AM EDT

Best for a no-Wi-Fi local alarm

Zircon Leak Alert 73938

$17.86 at Amazon

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Price as of Oct 24, 2026, 5:30 AM EDT

Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.

The 920-004 makes sense when your next concern is water reaching one specific place. Moen includes a 48-inch remote sensing disc with the single detector. You can keep the body accessible and put the disc into a low space, rather than squeeze the entire detector beneath a cabinet.

The distinction from the calculator matters. A moisture alert tells you water reached the sensor. It does not tell you gallons per minute, how long a leak ran before the alert, or what rate your utility charges. Keep your container or meter measurement if you want a bill estimate.

Moen’s specification lists a CR123A lithium cell as included and allows standalone detector use. It also lists 2.4 GHz Wi-Fi for the connected setup. Check that connection at the proposed position before you rely on a phone notification while you are away from the house.

Place the remote disc where it can encounter the leak you are watching. Moen describes the disc as suitable for low-profile or hard-to-reach areas. That does not make a sensor beneath one sink a monitor for every concealed pipe in the building. Its location sets its useful coverage.

The optional automatic response needs another product. Moen says the detector can trigger a Flo smart water shutoff already installed on the main. Buying this one-pack alone does not add that valve. The 48-inch disc included here is also different from Moen’s separately sold 6-foot sensing cable.

A toilet leak that sends tank water into the bowl may never wet a nearby floor sensor. Use a meter check and the EPA dye test for that question, then identify the toilet’s repair part. Do not substitute an under-sink moisture alarm for diagnosis of tank-to-bowl water loss.

Amazon listed model 920-004 as a one-pack sold by Amazon.com in New condition and in stock on Oct 22, 2026 at 6:10 AM EDT. Keep the model and pack size together when you compare the listing with the box. Extra detectors change placement coverage, not the function of this single unit.

Consider the 900-001 when you want the main monitored and a valve able to close, rather than an alarm at one puddle. Moen lists real-time flow readings along with automatic, remote and manual water control. Those are different jobs from the 920-004 detector’s moisture sensing.

Start with fit. The 900-001 specification lists 3/4-inch NPT brass tailpieces and an accessible cold-water main. The plumber needs to identify the meter, manual shutoff and pressure regulator, if present. A matching thread size alone does not settle the installation layout or the branches this valve can safely control.

The maker prohibits this device on piping that supplies residential fire sprinklers downstream. That is a reason to stop the purchase and ask the installer about the actual branch arrangement. Do not use a household leak-cost estimate to decide whether a shared domestic and fire supply can be shut automatically.

Moen’s INS11955C adds a second stop: DO NOT install the Flo device if any part of the upstream system contains galvanized piping.

For connected setup, the installation guide specifies 2.4 GHz Wi-Fi and continuously powered AC. There is a document conflict over outlet reach: the older specification says six feet, while INS11955C says ten feet. Have Moen and the installer resolve the instructions applicable to the unit, rather than improvise a mains extension cord.

INS11955C lists 125 psi maximum continuous pressure and recommends 80 psi or lower; the older sheet lists 175 psi maximum operating pressure. Have the plumber resolve applicable limits. Follow Moen’s main-water shutoff, draining, pressure-relief and safety-glasses steps before pipe work.

During Learning Mode, Moen states: System alerts and automatic shutoff feature will be temporarily unavailable. Do not rely on automatic protection during that period. You can still track water use and turn the supply on or off, according to INS11955C, page 10.

Without internet, a powered device enters Local Mode and can shut off water frequently. The manual says connecting to the internet is the way out of that mode. Check connectivity at the proposed installation location before relying on the system.

Do not bury the 900-001 or its power supply. Moen requires an ambient temperature from 32 to 140 °F (0 to 60 °C) and an off-ground power supply. Have the installer check the location against these limits.

Amazon listed the 900-001 as sold by Amazon.com, New and in stock on Oct 22, 2026 at 6:10 AM EDT. Keep the separately recalled 920-001 lithium-ion battery backup out of the order. CPSC’s notice concerns that accessory; it does not say the 900-001 main shutoff itself was recalled.

The Leak Alert is the simplest of the three. Zircon describes it as a self-contained, battery-powered unit that sounds a loud alarm the moment it gets wet. There’s no app, hub or Wi-Fi network to set up: fit one 9V alkaline battery, which isn’t included, and set it where water would collect.

Zircon rates the alarm at 90 dB and says it keeps sounding until the battery runs down. If the floor floods, the unit floats and keeps sounding. A low-battery beep tells you when to change the 9V. The body is 1.38 by 2.40 by 4.28 in. and weighs 2.4 oz. without the battery, small enough to sit beside a water heater pan or behind a toilet.

Its limit is the same as any local alarm: someone has to hear it. It can’t text you at work, it doesn’t measure flow, and it can’t close a valve. For the calculator above, it won’t give you a gallons-per-minute figure; it only tells you water has reached the floor at that spot.

Zircon lists an operating range of 20 to 105°F and 5 to 90% relative humidity, non-condensing, so check the spot before you leave it in an unheated crawlspace or garage. Zircon covers it under its Limited Lifetime Warranty for the United States and Canada.

The Amazon feature list ends with a line about three detectors, while the title and photo show one; Zircon sells a separate 3-pack. The offer showed it new and in stock from Amazon.com on Oct 22, 2026.

Device and job	What it detects	Automatic shutoff	Fit limit	Amazon
Moen 920-004 Remote-disc moisture sensing	Water at the base or 48-inch disc	Requires a separate installed Flo shutoff	Not a flow meter	Check price on Amazon
Moen Flo 900-001 Main-line monitoring	Flow through the installed main	Valve included	Cold main; power; fire-sprinkler restriction	Check price on Amazon
Zircon Leak Alert Local audible alarm	Water touching its metal contacts	No; it sounds a 90 dB alarm	Someone must hear it; 9V battery	Check price on Amazon
Measure first; no device purchase	Container volume or no-use meter difference	No	Requires a safe measurement point	Use the calculator above

For a running toilet, buying any of these monitors before identifying the tank problem adds a separate device without fixing the failed part. Our flapper versus fill valve comparison helps separate those repair paths. Keep the water-loss calculation separate from the repair quotation.

1. 1
   Collect only a safely reachable drip

   Use a marked container beneath a cold-water drip without loosening a fitting. Start a timer, catch the water, and record its volume. Do not touch hot water, appliance wiring or pressurized joints to get a measurement.

2. 2
   Enter the actual interval

   If you collect 250 mL in 60 seconds, select container, milliliters and seconds. The calculator converts that interval to US gallons per minute. A longer collection can make a tiny volume easier to read, if the leak stays steady.

3. 3
   Use the meter when collection is impractical

   EPA recommends comparing meter readings over two hours with no water use. Record all displayed digits, the time and the display unit. Do not open utility seals or operate a utility-owned curb valve.

4. 4
   Remove other water uses from the interval

   Avoid fixture use during the meter check and account for scheduled equipment such as irrigation. If normal demand occurs, the difference cannot be assigned entirely to a leak. Repeat under conditions you can verify.

5. 5
   Check the second reading before extrapolating

   Enter the later number as the second reading. A lower value needs investigation of units, reading error or rollover. The calculator rejects it rather than turn a negative meter difference into a water-loss estimate.

A meter can reveal unexplained water use without telling you which fitting is responsible. Keep the two readings and their timestamps. If the dial moves during a no-use interval, use that evidence to start diagnosis; do not treat the interval alone as proof that a particular toilet needs a flapper.

A reading of zero over one interval only describes that interval and the meter’s readable resolution. An intermittent toilet refill might occur later. Repeat when the suspected event is happening, or ask the utility whether its usage portal provides shorter intervals that help narrow the timing.

These are calculated examples, not field measurements. Every row assumes continuous flow for seven days, with hypothetical water and sewer rates of $6 each per 1,000 US gallons. The CCF row uses EPA’s rounded 748-gallon conversion. Your bill may use a more precise factor.

Combined charges use the unrounded flow. Adding rounded component charges can differ by one cent. Thirty days is a comparison interval, not the length of every billing cycle.

Try the four-gallon meter example in the tool: a first reading of 100, a second reading of 104, and 30 minutes. That becomes 192 US gallons per day. Seven days means 1,344 gallons; the two hypothetical $6 rates produce $16.13 combined after rounding.

Now keep the same meter measurement and set both utility rates to zero. Water loss stays 1,344 gallons over seven days and the added charge becomes zero. That is a valid result when confirmed by billing rules. Leaving a rate blank instead means the corresponding charge is unknown.

Look for the variable water line in your billing detail or current rate schedule. EPA distinguishes fixed service charges from charges that change with the volume used. Dividing the whole bill by total gallons can fold an unchanged base fee into the apparent rate and overstate the added leak charge.

Match each amount to its unit before entering it. A tariff stated per CCF is not a tariff per 1,000 gallons. Select the CCF option rather than copy the number into the 1,000-gallon field. The calculator uses about 748 US gallons per CCF, consistent with EPA’s billing explanation.

For increasing-block rates, the next gallon may land in a different tier from the first gallon already billed. This tool holds one entered rate constant. Calculate each known tier’s portion separately or ask the utility for a bill reconstruction if the leak crossed a tier boundary.

A seasonal rate can change during a long leak. Break the duration at the rate-change date and run each period using the relevant schedule. The resulting sum is still a volume-charge estimate; it does not automatically include minimum bills, taxes, surcharges or a utility’s rounding practices.

EPA explains that many utilities use incoming metered water to calculate sewer volume. Water that escapes outdoors can therefore affect both lines on a bill under that arrangement. Whether your utility adjusts the sewer portion for a documented leak is a local billing question, not something the destination of the water settles by itself.

Ask the utility which rate applies to the extra metered volume and whether a cap, fixed amount or seasonal average changes the calculation. Choose no added sewer charge only after that answer is clear. Otherwise leave sewer unknown so the tool does not quietly show an incomplete figure as the total.

Read the unit on the meter itself. A bill can summarize usage in CCF while the meter display shows cubic feet, or convert a metric reading to a billed unit. Entering a raw cubic-foot reading as CCF multiplies the estimate by about 100. Write the display unit alongside both readings.

The CCF conversion is rounded to 748 gallons in the tool so the calculation matches EPA’s household billing explanation. Cubic feet use the more precise volume conversion. These two options can differ slightly for the same physical volume; follow the factor your utility uses when reconciling an actual bill.

EPA’s examples show how much a steady toilet leak can vary. They do not let you diagnose 0.02 versus 0.2 gallons per minute by the sound of a refill. Pick an example only for an illustration, and replace it with a meter measurement when you need a household estimate.

Counted drips add another uncertainty: drop volume. USGS Drip Accumulator describes a small drip as approximately 0.33 mL. You can edit that assumption in the calculator. A different faucet outlet or dripping pattern can produce a different volume, so the same drip count need not mean the same water loss.

For an accessible drip, catching the water is more useful than arguing about a universal drops-per-gallon figure. Record milliliters and seconds directly. Never loosen a pressurized joint, approach exposed wiring or handle scalding water merely to obtain a sample. Use the meter or call a plumber when collection is unsafe.

An annualized figure answers a conditional question: what if this daily pattern continued for 365 days at the same rates? It is not a claim that those gallons have already escaped. Keep the period result when discussing a seven-day incident with the utility; use the annualized figure only to understand persistence.

If you cannot date the start, run two honest duration scenarios, such as the earliest possible date and the first confirmed observation. Label both as assumptions. A precise-looking dollar result does not make an uncertain starting date precise, and it should not become an unsupported refund request.

For toilet parts, confirm the model and flush-valve size before ordering. The existing toilet flapper guide and toilet fill valve guide cover different parts. A dye result establishes tank-to-bowl leakage; it does not prove every fault is fixed by the same replacement flapper.

A small calculated water charge does not establish that a leak is safe to leave. Water beneath a cabinet and water escaping into a wall can create very different repair situations at the same measured flow. Stop the supply if safely accessible and arrange the appropriate repair before returning to bill arithmetic.

The Amazon titles and maker specifications agree on the numbers for both picks. The outlet distance is a maker-document conflict. Do not treat title omissions as evidence of a different specification.

The seven-day examples use deliberately hypothetical utility rates, not national averages or current city tariffs. For an existing city’s rate discussion, see water leak costs by city and verify its date before using a number. Your current bill and utility schedule determine the inputs for your own estimate.

Sources

• EPA WaterSense, Understanding Your Water Bill, billing units and fixed/variable rate sections; read October 20, 2026.
• EPA WaterSense, Fix a Leak Week, Checking for Leaks; read October 20, 2026.
• EPA 832-F-23-003, WaterSense at Work section 2.2, November 2023, table 1, printed page 1.
• NIST Special Publication 811, Appendix B.8, US liquid gallon and cubic-unit conversions; Handbook 44 appendix C, 231 cubic inches per US gallon.
• USGS Water Science School, Drip Accumulator, approximate 0.33 mL small-drop assumption; read October 20, 2026.
• Moen 920-004sp, Smart Water Detector specifications, 4/20, page 1.
• Moen 900-001sp, Smart Home Water Monitoring and Leak Detection System specifications, rev.9/22, page 1.
• Moen INS11955C, 01/25, installation requirements, Local Mode and ambient limits, page 2; pressure limits, page 3; safety steps, pages 5 and 9; Learning Mode, page 10. Read October 20, 2026.
• Zircon Leak Alert 73938 product page: description, features, specifications and warranty; zircon.com, read Oct 22, 2026.
• CPSC recall 23-178, Flo Smart Water Monitor lithium-ion battery backups, April 13, 2023; read October 20, 2026. No Zircon Leak Alert recall found, Oct 22, 2026.
• CDC, Safety Guidelines: Reentering Your Flooded Home, electrical safety precautions; read October 20, 2026.
• Amazon Creators API, Oct 22, 2026, 6:10 AM EDT: title, seller, condition and availability for B0855BFQCZ, B00C03D01Q and B09DDG57X8, all new and in stock from Amazon.com. Product photos: Oct 20 and 22, 2026.