Quick Answer
A sudden increase in your water bill usually means either more water was used or water is flowing somewhere you did not intend. Plumbing causes can include a running toilet, leaking fixture, irrigation problem, underground supply leak or concealed leak. If your normal habits have not changed, start by checking whether water is moving through the meter while fixtures and water-using appliances are off.
Start by ruling out normal usage
Before assuming a leak, account for the billing period itself. Water use rises quickly with guests in the house, extra laundry, a new irrigation schedule, filling or topping off a pool, pressure washing, a new landscape install that needs daily watering, or a hot stretch of weather that doubles outdoor watering.
Compare the bill to the same month last year rather than to last month. Utility billing periods also vary in length, and a bill covering a few extra days can look higher without anything being wrong.
If nothing in your routine explains the increase, the plumbing system deserves a closer look.
Check whether water is still being used
This is the single most useful test a homeowner can run. Turn off every faucet, confirm the washing machine and dishwasher are not running, and avoid flushing for a few minutes. Ice makers, water softeners in a regeneration cycle, and irrigation controllers can all use water on their own, so factor those in.
Then look at the water meter. Many meters have a small dial or triangular indicator that spins with even a light flow. If it continues registering usage with everything off, water is still moving somewhere in the system.
Common plumbing causes and how to tell them apart
Different causes leave different clues, which is what makes the pattern useful.
Likely causes worth separating
- Running toilet: flow may be quiet or intermittent, and often shows up as a bill increase with no wet areas anywhere in the home.
- Dripping or leaking fixture: usually visible, and rarely large enough on its own to double a bill.
- Irrigation leak or stuck valve: wet or unusually green areas outdoors, often worse after a watering cycle.
- Underground water service leak: continuous meter movement, sometimes a soft or wet area between the meter and the house, sometimes no surface evidence at all.
- Concealed leak inside the home: damp drywall, staining, musty odor, a warm spot on a slab floor or the sound of water running with fixtures off.
- Water heater or connection leak: moisture at or around the unit and its piping.
What you can check first
- Read the meter, wait an hour with no water use, then read it again and note the difference.
- Add a few drops of food coloring to each toilet tank and check the bowl 15 minutes later without flushing. Color in the bowl means water is passing through.
- Walk the yard and look for wet, soft, sinking or unusually green areas, especially along the line from the meter to the house.
- Look under sinks, behind toilets and around the water heater for moisture or staining.
- Turn the irrigation controller off for a full day and see whether meter movement changes.
- Write down when the increase started and whether anything changed in the household that week.
Every one of these observations is safe, requires no tools and gives a plumber a real head start.
What not to do
- Do not dig in the yard to chase a suspected line before underground utilities have been located.
- Do not ignore a bill increase because nothing is visibly wet. Most underground and slab leaks never show on the surface.
- Do not assume the utility misread the meter without running the meter test yourself first.
- Do not open walls or ceilings based on a guess about where the water is traveling.
What Andy looks for
- Meter behavior over a measured interval with fixtures isolated
- Static water pressure and whether pressure holds when the supply is shut
- Toilet flappers, fill valves and supply stops
- Accessible piping, water heater connections and shutoff valves for moisture or corrosion
- Irrigation zones and any separate irrigation connection
- Signs of moisture on slab floors, baseboards, cabinet bases and exterior walls
Several of these overlap with the STAR Method inspection points for corrosion, water damage and water pressure.
Read about the five-point STAR MethodWhen to watch it and when to call
- Watch it
- The increase is small, you can point to a specific change in household use, and the meter is still with everything off.
- Schedule an inspection
- The bill rose with no change in habits, the meter keeps moving with fixtures off, or you see damp areas, staining or unexplained pressure changes.
- Call right away
- Water is pooling, you hear water running continuously inside a wall or under the floor, or a floor area is warm and wet.
Bottom Line
A sudden high bill points to either extra use or water escaping the system. Rule out household changes, then run the meter test and the toilet dye test. If the meter keeps moving with everything off, or you see moisture with no explanation, that is the point where locating the source is worth doing before anything gets opened or dug.
Related questions homeowners ask
How much water can a running toilet waste?
Enough to change a bill noticeably. A flapper that does not seal lets water move continuously from tank to bowl, and the flow is often too quiet to notice from another room.
Can a leak raise my bill without anything getting wet inside?
Yes. Water service leaks between the meter and the home, and some slab leaks, drain into the soil and never appear indoors.
Should I call the water utility first?
It can help to confirm the reading and ask whether the meter was estimated. If the meter shows flow with your fixtures off, the plumbing on your side of the meter is the next thing to evaluate.
Relevant service: Leak Detection
Investigate visible and concealed water loss that may contribute to property damage or high water bills.
Learn about Leak DetectionReviewed by
Andy Fauver
Texan Plumbing Pros
13+ years of plumbing and leak detection experience
Published September 16, 2026. Last reviewed September 16, 2026.