The bill itself
Start With the Bill Itself
Before looking for leaks, read the bill closely. The answer is sometimes on the page.
- Compare the billed usage, not just the dollar amount, with past periods.
- Check how many days the billing period covers.
- Look for notes saying the reading was estimated.
- See whether rates or fees changed.
- Compare with the same season last year, not just last month.
If the usage number is normal, the higher cost may come from rates or the billing period rather than a leak.
Common causes
Common Causes of Higher Usage
Use this checklist to rule out everyday explanations.
- Guests, a new household member or more laundry.
- Filling a pool, hot tub or large container.
- Lawn watering or a new landscape bed.
- An irrigation timer set wrong or a broken sprinkler head.
- A toilet that runs, refills on its own or has a worn flapper.
- A dripping faucet, showerhead or outdoor spigot.
- A water softener stuck in a regeneration cycle.
- A humidifier or other appliance connected to the water supply.
- Washing cars or power washing.
If several of these apply, the bill may simply reflect what happened that month.
Toilets
Toilets: A Common Silent Culprit
A leaking toilet can run without making much noise. It may waste water all day and night.
Put a few drops of food coloring in the tank and wait about 15 to 30 minutes without flushing. Color in the bowl means water is leaking through.
Also listen for a toilet that refills by itself between uses. That is another sign of an internal leak.
Irrigation & outdoor
Irrigation and Outdoor Use
Outdoor watering can raise usage quickly, especially in summer. A timer that runs too long or a damaged line can add up without anyone noticing.
Check controller settings and walk the yard while zones run. Look for soggy spots, geysers or heads that don’t pop up.
Irrigation repair is a separate trade. If the problem is in the sprinkler system, an irrigation specialist is usually the right call.
Estimated reads
Estimated Reads and Meter Questions
If a bill was based on an estimated reading, the next actual read can cause a catch-up charge. That can look like a sudden spike.
If you believe the meter itself is misreading, contact your water utility. They are the right party for meter accuracy and billing questions.
Meter test
Confirm With a Meter Test
The most useful next step is a meter test. Turn off all water use and watch whether the meter keeps moving.
Our guide on how to check a water meter for leaks walks through each step and how to read the results.
If the meter is still with everything off, a continuous leak is less likely. If it moves, keep investigating.
Hidden leak signs
Signs That Point to a Hidden Leak
When usage stays high and the obvious causes are ruled out, look for subtler clues.
- The sound of running water when nothing is on.
- Warm spots on a floor, which may suggest a hot water line leak.
- Damp, musty odors or stains on walls or ceilings.
- Low water pressure that wasn’t there before.
- Wet, soft or unusually green patches along the water line route outside.
Our guide to signs of a hidden water leak covers these clues by room.
What to do next
What You Observe and What to Do Next
| What you observe | Most likely direction | Next step |
|---|---|---|
| Usage normal, cost higher | Rates or billing period changed | Review the bill or ask your utility |
| Bill notes an estimated read | Possible catch-up charge | Compare with the next actual reading |
| Usage high, meter still with water off | Higher use, not a constant leak | Review household and outdoor use |
| Toilet dye test positive | Toilet leak | Repair the toilet and retest |
| Meter moves with all water off | Ongoing leak somewhere | Check fixtures, then consider hidden water leak detection |
| Wet or sinking yard along the line route | Possible buried line leak | See underground water line leaks |
| Water at the meter connections | Possible meter-area leak | Contact the City Water Utility |
| High usage only in summer | Irrigation or outdoor use | Check timers and zones |
Underground leaks
When the Leak May Be Underground
Not every leak shows indoors. A leak on the buried line can soak into soil without obvious signs.
Whether it shows on your meter depends on where the meter sits relative to the leak. If your meter is indoors, a leak on the line before it may not register.
The City of Naperville explains which meter leaks it repairs on its water meter leaks page. Our Naperville water line responsibility guide explains the boundaries in more detail.
Keep a record
Keep a Simple Record
Notes help whoever investigates next. They also help with any billing conversation.
- Save recent bills showing usage over several periods.
- Record meter readings with the date and time.
- Note any changes in household or outdoor use.
- Photograph any stains, wet spots or soggy ground.
FAQ
Frequently Asked Questions
Does a high water bill always mean I have a leak?
No. Usage changes, irrigation, estimated reads and rate changes can all raise a bill. A meter test helps you tell the difference.
Can a leak raise my bill without any water showing?
Yes. Toilet leaks go down the drain, and some pipe leaks drain into soil or under a slab. That is why a meter test matters.
Who should I contact about a billing dispute?
Contact your water utility. They handle meter accuracy, readings and billing questions.
What if my meter test is fine but my bill is still high?
The leak may be intermittent, or usage may be the cause. Repeat the test at different times and review outdoor and appliance use.
Get help
Get Help With a Leak You Can’t Find
More troubleshooting is available in our water leak guides. If your meter shows water loss and you can’t find the source, a professional leak investigation can narrow it down.