A sudden jump in your water bill usually means a leak. The most common culprit is a running toilet, followed by dripping faucets, leaking irrigation and hidden leaks in walls, slabs or the buried service line. To confirm a leak, turn off all water, note the reading on your water meter, and check whether it moves over the next hour.
Reviewed by Ron Olsen, Master Plumber, certified in Washington
Where the Extra Water Is Going
- Running toilet
- A worn flapper or a faulty fill valve can waste a large amount of water without being noticed.
- Dripping faucets and shower heads
- Small drips add up over a month.
- Irrigation leaks
- Broken sprinkler heads or lines can leak underground.
- Hidden leaks
- Leaks inside walls, under a slab or in the service line from the meter.
- Billing or meter issues
- A misread or faulty meter can also explain a spike. Compare the readings with your bill.
What You Can Safely Check
- Turn off every faucet and water-using appliance, note the meter reading, and check it again an hour later.
- Put a few drops of food coloring in the toilet tank. If color shows in the bowl within 15 minutes without flushing, the flapper is leaking.
- Check under sinks, around the water heater and at outdoor spigots.
- Shut the main valve and check the meter. If it still moves, the leak is between the meter and the house.
When to Call a Plumber
Call a plumber if the meter moves with everything off and you can't find the cause, or if you see warm spots on floors, damp walls or wet patches in the yard. Professional leak detection pinpoints hidden leaks without unnecessary demolition.
The repair is usually part of leak detection & repair, which explains what the plumber does and what affects the cost.
Slab Leaks by City
What our city pages say about slab leaks:
- Corpus Christi, TX: Supply line leaks under slab foundations show up as warm floors or high water bills.
- Mission Viejo, CA: Copper under 1970s and 1980s slabs pinholes with age.
- Queen Creek, AZ: Lines under the slab leak unseen until a floor is warm or the bill jumps.
- Naples, FL: Lines under the slab leak unseen until a floor is warm or the bill jumps.
- Enterprise, NV: Lines under the slab can pinhole or wear where they rub the concrete.
- Broken Arrow, OK: Clay soil shifts and cracks lines under the slab.
- Bossier City, LA: Clay soil shifts and stresses lines under the slab.
- Hurricane, UT: Lines under the slab leak unseen until a floor is warm or the bill jumps.
High Water Bill Questions
Will my water utility adjust the bill for a leak?
Many utilities will adjust the bill once after the leak is repaired. Ask your utility what proof they need, such as a plumber's invoice.
Can a toilet really raise my water bill that much?
Yes. A toilet that runs constantly can waste more water than everything else in the house combined.