The Water Bill From a Toilet Nobody Heard Running
Why this matters
A water leak bills twice. Every gallon that runs through the meter is charged as water, and on most residential accounts the sewer charge is computed from the same gallons, so a leak that runs all day is paid for on both lines until somebody finds it. It also keeps running while the shop is deciding what to do, which makes this one of the few high-bill calls where the first job is to stop the loss and the second is to explain it.
The customer in this case had no visible leak, no wet floor, no sound of running water, and a bill twice the usual. The leak was in a bathroom nobody used, and it made no noise at all.
The signal
The customer called on a Monday afternoon with a two-month water and sewer bill in hand. Water use was billed in CCF, hundreds of cubic feet; one CCF is about 748 gallons (see related: Water and Sewer Bills: Gallons, CCF and the Winter Average, which owns the conversions).
- This bill: 18 CCF over 61 days. 18 x 748 = 13,464 gallons, or 13,464 / 61 = 220.7 gallons a day.
- Same period last year: 9 CCF over 62 days. 9 x 748 = 6,732 gallons, or 6,732 / 62 = 108.6 gallons a day.
Per day, use had risen by 220.7 minus 108.6 = 112.1 gallons, a factor of 2.03. Two adults, no new fixtures, no irrigation, no pool. Both reads were actual, and the account history showed the bills before this one sitting near last year's level, so whatever started had started recently.
One caution that applies to every CCF bill: utilities usually bill whole units, so each bill can be off by up to one CCF, 748 gallons, depending on where the register sat at read time. A one-unit difference means nothing. A doubling does.
Stopping it before explaining it
Before the office booked anyone, it walked the customer to the meter by phone (the script belongs to How to Walk a Customer Through a Water Meter Leak Check by Phone). The meter was in the basement, read in gallons, and had a small low-flow indicator, a star- or triangle-shaped dial that spins at flows too small to move the main hand. With every tap off, the dishwasher and washer idle and nobody flushing, the indicator was turning slowly. Water was moving through the meter with nothing open.
At roughly 112 gallons a day, the loss is about 4.7 gallons an hour, every hour, and the cost of each day's wait is measurable: about 0.15 CCF of water and the same again on the sewer side. The options, priced in what each gives up:
| Option | Stops the loss | What it costs |
|---|---|---|
| Close the main valve at night | Overnight only | No water at night, and every fixture goes quiet at once, so nothing is learned about which one |
| Close every toilet stop now | Yes, if a toilet is the leak | Says nothing about which toilet, and loses the rate |
| One more night open, then close stops one at a time | After about 15 hours | About 70 gallons more, and in return the leak's rate and its location |
The office picked the third. One more night of loss, about 4.7 gallons an hour for the 15 hours until the morning isolation, roughly 70 gallons or 0.1 CCF, buys the one number that later tells you whether the leak you find explains the bill. Shut everything off first and you can find a leak but never prove it was THE leak.
Before touching any valve: the customer was told where the main shutoff was and to find it first. Fixture stops under toilets are often old multi-turn valves. Turn them gently clockwise by hand; if one drips from the stem when turned, put a towel under it and leave it for the plumber rather than forcing it, because a stop that snaps on a pressurized line floods the room, and the main is what stops that.
The overnight record
The customer ran the overnight read that night and the isolation the next morning, and sent a photo of the meter face at each read.
METER LOG - 2 Larch Ct basement meter, gallons
Household: no water used 10:30 PM - 6:30 AM
Softener display: last regeneration 4 days ago
Fridge ice maker: valve closed for the test
TIME READ (gal) NOTES
10:30 PM 482,316.4 low-flow dial turning
6:30 AM 482,353.2 low-flow dial turning
OVERNIGHT 36.8 gal in 8.0 h = 4.6 gal/h
ISOLATION, 20 min each, one stop closed at a time
Hall bath toilet 1.5 gal reopened
Primary bath toilet 1.6 gal reopened
Guest bath toilet 0.0 gal left closed
Reading the overnight line. 482,353.2 minus 482,316.4 is 36.8 gallons over 8 hours, 4.6 gallons an hour. Run that across a full day and it is 4.6 x 24 = 110.4 gallons a day. Across the 61-day bill it is 110.4 x 61 = 6,734 gallons.
Checking it against the bill. The bill's excess over last year's rate was the total, 13,464 gallons, minus what the house would have used at 108.6 a day for 61 days, 108.6 x 61 = 6,624 gallons, which leaves 13,464 minus 6,624 = 6,840 gallons. The overnight rate accounts for 6,734 of those, or about 98 percent. The remaining 106 gallons is far inside the one-CCF rounding on a single bill. The leak's rate, measured with nothing else running, explains the bill on its own.
Why the softener and ice maker lines matter. A water softener that regenerates overnight uses tens of gallons in one go, and an overnight read taken on a regeneration night would have overstated the leak. The display said four days ago, so not that night. The ice maker valve was closed so a refill could not land in the window.
Reading the isolation. At 4.6 gallons an hour, 20 minutes should move the meter about 1.5 gallons. Closing the hall bath stop left 1.5 gallons moving; closing the primary bath stop left 1.6. Neither was the leak. Closing the guest bath stop dropped it to zero and stopped the low-flow dial. The stop stayed closed: the loss was contained, and the customer could still open it to fill the tank and close it again if anyone needed that toilet before the repair.
Why nobody heard it
The guest bathroom was at the end of the upstairs hall, its door kept shut, the toilet used a few times a year. That explains why nobody noticed, but not why it was silent.
Most people know a running toilet as the one that hisses and refills every few minutes. That is a fast leak: water drains past the flapper (the rubber seal at the bottom of the tank that lifts to flush) faster than a trickle, the tank level drops, and the fill valve opens fully with a rush. A slow enough seep never drops the level far. The fill valve opens just a crack and replaces water at the rate it leaves, quietly and continuously. At 4.6 gallons an hour, which is less than a tenth of a gallon a minute, there is no hiss, no refill cycle and nothing visible in the bowl except, on a close look, a faint ripple at the rim.
The plumber's trace
The plumber arrived Tuesday afternoon with the meter log already in the ticket, and did the confirming steps in an order that rules things out rather than assuming them.
- Overflow first. With the stop opened and the tank refilled, the water level sat about an inch below the top of the overflow tube. Water running down the overflow would point at the fill valve; this was not that.
- Dye test. Ten drops of food coloring in the tank, no flush, a twenty-minute wait. The bowl water turned blue. Water was passing the flapper.
- The flapper itself. The rubber had hardened and curled at one edge, and the seat under it carried a mineral ring. An in-tank bowl-cleaning tablet had been sitting in the tank for well over a year; chemicals released in the tank are a common reason flappers age early, and the customer had forgotten it was there.
The flapper was replaced, the seat cleaned, the tablet removed and the stop reopened. The repair itself follows the shop's Running Toilet Diagnosis and Repair procedure. Before leaving, the plumber watched the reopened stop's stem and the supply connection for drips, confirmed the tank refilled and shut off at its marked level, and ran a second dye test: bowl clear after twenty minutes.
The confirmation that matters. That night the customer ran the overnight read again: 0.0 gallons in 8 hours, low-flow dial still. A clean dye test proves the flapper seals. Only the meter proves the house has no other leak.
The bill that stays after the leak is fixed
Two questions for the utility, which the customer asked and the shop did not answer for them.
Leak adjustment. Many water utilities will adjust a bill for a repaired leak, and the terms vary widely by utility: some require a dated repair receipt within a set number of days of the bill, some allow one adjustment per account per year or longer, and some adjust only the sewer portion for leaks whose water never reached the sewer, which a toilet leak did. The shop gave the customer the dated repair invoice and both overnight meter logs, before and after, and told her to ask what her utility's policy is. It did not tell her she would get anything back.
The sewer average. Some utilities set the residential sewer charge for the whole year from water use in a set of winter months, the "winter average". If this bill fell inside that window, the leak may be setting the sewer charge for months after it was fixed. That is worth asking about specifically, and asking for a recalculation if it applies. The mechanics are in Water and Sewer Bills: Gallons, CCF and the Winter Average.
What the shop changed
The case reached the shop as a billing call, but it had been in front of a plumber three months earlier: the same customer had a kitchen faucet replaced in the fall. Nobody had looked at a toilet that day, because nobody had asked.
The shop added a dye check to every plumbing visit where the house has toilets. A few drops in each tank on arrival, bowls checked before leaving, one line on the ticket per toilet: clear, or blue. It takes about a minute per toilet, on a visit where the tech is in the house anyway, and it finds exactly the leak this case was about: silent, slow, and in the room nobody uses.
References
- See related: Water and Sewer Bills: Gallons, CCF and the Winter Average
- See related: How to Walk a Customer Through a Water Meter Leak Check by Phone
- See related: Reading Water Meter + Leak Detection Reference
- See related: Running Toilet Diagnosis and Repair
- Your water utility's published leak adjustment and sewer billing policies