Why Your Water Bill Suddenly Went Up
Start with the meter test: read it, use no water for an hour, read it again. Then dye-test every toilet, because a failed flapper wastes up to 200 gallons a day and is the most common cause by a wide margin. Then rule out irrigation. Then call for leak detection.
Diagnose it in order of likelihood
The causes of a sudden bill increase are not equally likely, and working through them in order saves money. Most people can find the problem themselves in half an hour without any equipment.
Run the meter test
Turn off every water-using fixture and appliance. Read the meter, wait an hour with no water use at all, and read again. Movement confirms a leak and tells you roughly how fast.
Dye-test every toilet
Add a few drops of food colouring to each tank and wait fifteen minutes without flushing. Colour appearing in the bowl means the flapper is leaking. This is the single most common cause.
Shut off irrigation entirely
Turn the irrigation system off at its valve for a full day and watch the meter. Underground irrigation leaks produce large losses with no visible symptom.
Check every visible fixture and connection
Under sinks, behind toilets, at the water heater, at the washing machine. Look for corrosion, mineral crust, and damp.
Check outdoor spigots and the meter box
A dripping hose bibb adds up, and standing water in the meter box points to a leak on the service line.
If the meter still moves, call for detection
At this point the leak is hidden: in a wall, under the slab, or in the buried service line. That needs acoustic equipment.
What each cause typically wastes
Scale helps prioritize. A running toilet is both the most common cause and one of the largest, which is why it is worth checking first.
- Running toilet: up to 200 gallons a day, and often more with a badly failed flapper
- Dripping faucet: 5 to 20 gallons a day, noticeable over a quarter but rarely dramatic
- Irrigation leak: highly variable, and frequently the largest single cause when present
- Pinhole supply leak in a wall: hundreds of gallons a day, plus hidden structural damage
- Slab leak: continuous, often thousands of gallons a month with no visible sign
- Service line leak between meter and house: continuous, and your responsibility rather than the utility's
Rule out the non-leak explanations too
Not every bill increase is a leak, and it is worth eliminating the innocent explanations before paying for detection.
Check whether the billing period was longer than usual, whether your utility changed rates, and whether the reading was estimated rather than actual, which produces a correction spike later. Seasonal irrigation, house guests, a new appliance, filling a pool, or a season of heavier laundry all show up as real usage.
If the meter test shows no movement with everything off, you do not have a leak, and the answer is in usage or billing rather than plumbing.
Frequently asked questions
How do I read my water meter for a leak test?
Most meters have a small triangular or star-shaped low-flow indicator that spins with even a tiny flow. With every fixture off, that indicator should be completely still. If it moves at all, water is leaving the system. For a digital meter, note the reading, wait an hour, and compare.
Could a high bill be the utility's error?
It happens, particularly with estimated readings or a faulty meter. If your own meter test shows nothing moving with all water off, you have good evidence the problem is not on your side. Most utilities will re-read or test the meter on request, and many will adjust a bill for a documented meter fault.
Who pays for a leak between the meter and my house?
You do, in nearly every jurisdiction. The utility owns the line up to and including the meter; everything from there to the house is the property owner's. Some utilities offer a one-time leak adjustment credit when a documented service line leak is repaired promptly, so it is worth asking.
Is it worth calling for leak detection or should I just watch it?
If the meter moves with everything off and you have ruled out toilets and irrigation, watching it costs money every day and risks hidden structural and mold damage. Detection typically runs $350 to $800 and routinely saves several times that by preventing demolition in the wrong place.
Related guides
- Slab Leak Warning SignsHow to recognize a leak under your foundation before it undermines the slab, and what to do once you suspect one.
- When to Call an Emergency Plumber (and When to Wait)After-hours plumbing costs 1.5 to 2 times standard rates. Here is which problems justify it and which are cheaper to schedule.
- What to Do When a Pipe BurstsThe first ten minutes after a pipe bursts determine most of the damage. Here is the order of operations that limits it.
- Frozen Pipes: What to Do Before They BurstA frozen pipe has not necessarily failed yet. Thawing it correctly, and being ready at the shutoff, is what keeps it from becoming a burst pipe.
Related services
- Emergency Leak DetectionNon-invasive location of hidden water leaks behind walls, under floors, and beneath slabs using acoustic, thermal, and pressure testing equipment.
- Slab Leak Detection and RepairLocation and repair of water lines leaking beneath a concrete foundation, using acoustic and thermal detection to minimize concrete work.
- Emergency Toilet RepairRepair of overflowing, leaking, or non-functioning toilets, including wax ring replacement, valve repair, and clearing blockages.
- Main Water Line RepairRepair and replacement of the buried water service line between the meter and the house, including trenchless replacement options.
Cost guides
- Burst Pipe Repair CostWhat burst pipe repair costs by location and pipe type, plus the water damage costs that usually exceed the plumbing.
- Water Heater Replacement CostWhat tank and tankless water heater replacement costs, including the code upgrades that appear on the invoice unexpectedly.
- Drain Cleaning CostWhat drain and sewer clearing costs by method and location, and when jetting is worth the premium over cabling.
Common questions
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- The Empty House Problem: Why Seasonal Properties Fail in WinterA thermostat setting is not winterization. Why vacant properties produce the most expensive freeze damage there is.