Spot the estimated-read fingerprint

Look for “estimated,” “E,” or “actual vs estimated” language on the prior bill or portal. A short, suspiciously round prior usage followed by a much larger actual period is the classic true-up pattern.

• Seattle Public Utilities: an estimated reading is marked with an asterisk (*) next to the meter reading for the last bill. SPU estimates when it cannot access the meter.
• New York City DEP: issues an estimated bill when it cannot get a reading, for example when the automated meter reading device fails to transmit. DEP says the meter is still recording your use, and you can check the estimated reading on the bill against the reading on your meter.
• Portland Water Bureau: says most single-family customers have their meters read once every three months, so one read can cover a long stretch of use.
• Denver Water: bills in 1,000-gallon increments and rounds down. If you use 2,999 gallons, you are billed for 2,000 and the remaining 999 gallons are charged on the next bill. That is a small, routine carry-over, not an error.

Normalize both periods to units per day

Divide each period’s units by its billing days. If daily use is similar across the two cycles, the dollar jump is mostly catch-up math — not a new continuous leak.

Worked example: how an estimate reconciles

This uses made-up readings for two-month billing periods. It follows the rule Seattle Public Utilities describes: if an estimate was too low, the difference shows up on the next bill. One CCF (hundred cubic feet) is 748 gallons, per EPA WaterSense.

1. Last actual read, end of February: meter at 1,250 CCF.
2. March–April bill (61 days) is estimated at 1,258 CCF, so it bills 8 CCF = 8 × 748 = 5,984 gallons, about 98 gallons a day.
3. May–June bill (61 days) has an actual read of 1,276 CCF. It bills from the estimated reading: 1,276 − 1,258 = 18 CCF = 13,464 gallons, about 221 gallons a day.
4. Check the total: 1,276 − 1,250 = 26 CCF over 122 days, and 8 + 18 = 26 CCF. That is 19,448 gallons, about 159 gallons a day across both bills. Nothing was billed twice.

If use was steady, each period really used about 13 CCF. The estimate was 5 CCF low, so the second bill carries 13 + 5 = 18 CCF. The jump from 98 to 221 gallons a day is the estimate being corrected, not a new leak. Your own utility's units, tiers, and billing periods will differ.

Still rule out a real leak

True-ups and leaks can coexist. Run a quiet-house meter check and dye-test toilets so you do not miss a flapper that started during the estimated window. EPA WaterSense suggests reading the meter before and after a two-hour period when no water is being used; if it changes at all, you probably have a leak.

Talk to the utility with evidence

Ask which reads were estimated vs actual, request a reread if the dial disagrees, and ask about bill averaging or payment plans. Bring portal screenshots and meter photos.

A true-up is a normal correction once an actual read replaces an estimate. A billing dispute fits only if the actual read itself looks wrong, for example if the reading on the bill is higher than what your meter shows. NYC DEP says customers who believe a bill is inaccurate can submit a formal appeal, and DEP staff will manually verify the bill and respond in writing.

If the catch-up bill is hard to pay, ask about a plan. As checked October 3, 2026, Seattle Public Utilities offers short-term plans of up to 60 days, and long-term plans through PromisePay for residential customers with a past-due balance of at least $100. On its service termination FAQ, NYC DEP says a payment agreement requires at least a 25% down payment and can be entered only by the owner or an authorized representative.