The bill is on the counter and the usage number is nearly double what it was two months ago. Nobody filled a pool, no one has moved in, and you have walked the whole house looking for a puddle and found nothing. A high water bill with no visible leak is one of the more maddening problems a homeowner faces, because the evidence is a number on paper and the cause is somewhere you cannot see. The water is going somewhere, though, and in a Las Vegas home there are about seven places it can go. Each has its own test, and most of the tests take minutes.

Work through them in order. The first two tell you whether there is a leak at all. The rest find it.

Read the bill before you read the meter

Start with the bill itself, because not every jump is a leak. The Las Vegas Valley Water District bills residential customers on a four-tier rate structure, so the more thousand-gallon units you use in a period, the more each additional unit is charged, and a modest rise in use can produce a larger rise in the total. The district also applies a seasonal excessive use charge above a usage threshold, which is why a summer bill can jump sharply even when habits have not changed much.

Compare the gallons, not the amount due, and check the read dates in case the billing period was longer than usual. Then compare this period's gallons to the same period last year, not to last month, because irrigation makes summer and winter use look like two different houses. If the gallons are flat and only the total went up, the answer is the rate tiers or the season. If the gallons jumped, keep going.

The two-hour meter test tells you whether water is moving

Find the meter box, usually in the sidewalk or the strip of ground beside it, and lift the lid. Turn off every fixture, the irrigation controller, the pool autofill, the ice maker and the softener if you can bypass it, and make sure nobody flushes anything. Then look at the meter face. Most have a small triangle, star or wheel that spins when any water passes. The U.S. Environmental Protection Agency's version of the test is simple: read the meter before and after a two-hour period when no water is being used, and if the reading changed at all, there is a leak.

If the indicator is turning, the water district's guidance adds a second step that splits the house from the yard: close the main shutoff valve at the house and look again. If the indicator stops, the leak is inside the house or under it. If it keeps turning, the leak is between the meter and the shutoff, in the service line or the irrigation connection. That one answer decides which of the sections below you read first.

If nothing is moving on the meter, there is no continuous leak, and you are looking for something that runs intermittently: an irrigation schedule, a softener regeneration cycle, a pool fill valve, or a toilet that only leaks sometimes.

Toilets leak silently, and more of them do than you would guess

The single most common cause of a high bill with no puddle is a toilet whose flapper no longer seals. Water trickles from the tank into the bowl and down the drain, the fill valve tops the tank up, and the cycle repeats all day without a sound. The water district's own leak page says more than 20 percent of gravity-flush toilets leak, and the EPA notes that a leaking flapper can waste thousands of gallons a year.

The test is food coloring. Put a few drops in the tank, do not flush, and wait. If color shows up in the bowl within ten minutes, the flapper is leaking. Do this on every toilet in the house, including the guest bathroom. The fix is a new flapper, which the EPA suggests replacing at least every five years, and our post on how to fix a running toilet walks through it. Hard water here corrodes flappers and fouls the seat they rest on faster than in most places, so a toilet that passed the dye test last year may not pass it now.

A fill valve set too high does the same thing by a different route: water rises above the overflow tube and runs straight down it. Lift the tank lid and look; the water line should sit below the top of the overflow tube.

Irrigation is the biggest water user in a Las Vegas yard and the easiest place to lose it

In this valley, outdoor use dwarfs indoor use for most homes with any planting at all, and the irrigation system is the one part of your plumbing that runs on a schedule you may not have looked at in a year. Check the controller first. A program that was set for a heat wave and never turned back down, a second program running without you knowing, or a start time that overlaps with another zone can add thousands of gallons a month without a single drop showing.

Then look for leaks in the system. The EPA gives a sobering figure: an irrigation leak just 1/32 of an inch across can waste about 6,300 gallons a month. Run each zone for a few minutes and walk it. Look for a geyser from a broken head, a soggy patch of rock or mulch where a drip line has split, a valve box with standing water in it, and a zone that keeps weeping after it shuts off, which means a valve that is not closing fully. The meter test confirms the yard: with the house shutoff closed, turn the irrigation valves off at the manifold and see whether the indicator stops.

Pools, softeners and the appliances that use water on their own

A pool with an automatic fill valve will replace whatever the pool loses, so a pool leak or a stuck float shows up on the water bill rather than as a dropping water line. Turn the autofill off and do the bucket test the water district describes: set a bucket of water on a pool step, mark both levels, and compare after a few days. If the pool level drops noticeably more than the bucket, the pool is losing water beyond evaporation, and the fill valve has been covering for it.

A water softener regenerates on a schedule and sends a lot of water to the drain each time. A softener stuck in regeneration, or set to regenerate far more often than the household needs, can add to the bill without any visible sign. Put the softener in bypass and run the meter test again; if the indicator stops, the softener was the mover.

The leaks that hide inside walls, under floors and under the house

If the house shutoff stops the meter but you have found no toilet, appliance or fixture at fault, the water is escaping from a pipe you cannot see. Under a sink cabinet, look for a dark stain or swollen particleboard around the supply stops. Behind a washing machine, feel the hoses and the wall. In a water heater closet, check the pan and the fittings. The post on fixing a leaky faucet covers the small, steady drips that add up; a faucet dripping once a second wastes more than 3,000 gallons a year according to the EPA.

Then consider the slab. Nearly every home here has water lines running under the concrete, and a pinhole in one of them sends water into the ground rather than onto a floor. A warm spot on the tile, the sound of running water in a quiet house, a water heater that seems to run constantly, and the meter turning with everything off are the signs that point there. That is a plumber's diagnosis with pressure testing and listening equipment, and Dwellness handles those leaks through its under slab leak add-on.

The service line between the meter and the house

If the meter keeps turning with the house shutoff closed and the irrigation off, the leak is in the service line, the pipe that runs from the meter to the house. In older neighborhoods that pipe may be galvanized steel or early plastic, and both fail with age. Look for a damp or sunken strip of ground along the likely path from the meter box to the front of the house, or a patch of weeds that is greener than everything around it. Repairing the service line means excavation, and it is covered separately from the plumbing inside the house, which is why Dwellness lists the exterior water service line as its own add-on.

What a home warranty covers once the cause is found

Reading the meter and dropping dye in a tank are the homeowner's part. The repairs behind a high bill are often warranty territory. Every Dwellness plan, including the Essential Plan, covers the plumbing system, which takes in the supply lines, stoppages, faucets and the components inside toilets that fail from normal wear and tear. The plumbing home warranty page lists what a typical plumbing claim includes. Under slab leaks and the exterior water service line are optional add-ons, and coverage can be adjusted for up to 30 days after the first payment, so a plan can be fitted to a slab home with a long front yard after the fact.

When a covered part fails, you file a service request online at any hour or call (702) 641-8888, pay the service fee for the trade, and a licensed local plumber is sent out; 97 percent of Dwellness claims are approved. Irrigation systems, the pool shell and the water itself sit outside a home warranty, as does a leak that was known about and left to run; pool and spa equipment is available as a separate add-on. The water district's customer assistance programs, mentioned on its leak page, are the place to ask about a bill adjustment once a leak has been repaired.

A bill that doubled with nothing to show for it is almost always a flapper, a drip line, a fill valve or a pipe you cannot see, and the meter test narrows that list to one in an afternoon. Fix the easy ones yourself, and let a plan handle the ones that need a plumber. Dwellness has covered Las Vegas plumbing for homeowners since 1986, and the fastest way to see what a plan would include for your home is to request a free quote at dwellness.house or call (702) 509-7007.

Frequently Asked Questions

The usual causes, in order of how often they turn out to be the answer, are a toilet flapper that no longer seals, an irrigation program or leak, a pool autofill valve covering for a pool leak, a water softener regenerating too often, and a hidden leak in a supply line or under the slab. A two-hour read of the meter shows whether water is moving continuously, which separates the first group from the rest.

Turn off every fixture, appliance and the irrigation, then watch the small flow indicator on the meter face. If it turns, water is moving. Close the main shutoff at the house and look again: a stopped indicator means the leak is inside or under the house, while one that keeps turning means the yard or the service line. The EPA suggests taking a reading, waiting two hours with no use, and reading again.

Yes. A flapper that does not seal lets water run from the tank to the bowl continuously, and the EPA describes toilet leaks as silently wasting thousands of gallons a year. The district's own figure is that one gravity-flush toilet in five leaks. A few drops of food coloring in the tank, and ten minutes of waiting, confirm or rule it out.

The bill itself is not covered, but the plumbing failures behind it often are. A Dwellness plan covers the home's plumbing system, including toilet components, supply lines and stoppages that wear out through normal use. Slab leaks and the service line out to the meter are add-on items. Irrigation leaks and leaks in the pool shell fall outside a home warranty, though pool and spa equipment can be covered as an add-on.

The Las Vegas Valley Water District's leak page points to its customer assistance programs, which include leak adjustment and reimbursement programs, and the district also notifies account holders when it detects continuous flow for three days or more. Keep the plumber's invoice or your own repair receipt, since an adjustment request will usually ask for evidence the leak was repaired.