Water Bill Spike Checks: Finding a Leak Before It Costs You

Start with the bill itself

Before you check anything in the house, compare the current bill with the same month last year, and with the last two or three bills. Seasonal change is normal. Lawn watering raises use in summer, and a household with guests or a new occupant will use more water. A spike that appears in only one billing period may be a reading error or a one-time event. A steady climb across several periods is more likely to point to a leak that has been running for a while.

Look at the meter reading printed on the bill and compare it with the reading on the meter itself. A mismatch can mean the bill was estimated, and an estimated bill can hide a real increase until a later reading catches up. If the utility offers online access to daily or monthly usage, check it. Patterns in the data often show whether the extra use happens at night, during the day or on a schedule.

Check the meter with everything off

The meter is the most reliable test in the house because it measures all water passing through the service line, regardless of which fixture is responsible. Turn off every faucet, the washing machine, the dishwasher and the outdoor hose. Make sure the ice maker is not refilling and that no one is running a shower. Then find the meter, which is often in a basement, a utility room or a box near the curb, and look at the leak indicator. Many meters have a small dial or a triangle that turns when any water is moving.

If the indicator still moves, or the register numbers change over the course of an hour, water is flowing somewhere in the system. Do not stop at this point. Water can be leaving through a toilet, an irrigation line, a buried supply pipe or a fixture that appears to be off. Record the time, the meter reading and the reading again an hour later. That record is useful information for any provider you call.

Check the toilets next

Toilets are the most common hidden source of extra water use in a home. A flapper that does not seal lets water run from the tank into the bowl, and the water is replaced continuously, so the meter keeps moving. The simplest test is to add a few drops of food coloring to the tank and wait without flushing. If color appears in the bowl within a short time, the flapper or the valve seat needs attention. Try this on each toilet, because one fixture can hide the problem for the others.

Listen for a toilet that refills by itself, a faint hiss from the tank, or a fill valve that never shuts off completely. Any of these can add a surprising amount of water over a month without any visible sign.

Then the faucets, outdoor lines and appliances

Look under each sink for drips that you can only see when the cabinet is open. Check the washing machine hoses for bulges or cracks, and make sure the dishwasher connection is dry. A water heater that is leaking at a fitting or a relief valve can waste water quietly, so look around its base and connections too.

Outdoors, check every hose bib and irrigation zone. A sprinkler head that is cracked or a valve that is stuck open can run for long periods without anyone noticing, especially if it is on a timer. Turn each irrigation zone on one at a time and watch for water where it should not be, such as a pooling area, a soft spot in the lawn or a constant trickle at a valve box.

What the checks tell you

If the meter stays still with everything off, the bill increase is more likely to come from usage in the house, a change in habits, or a reading issue with the bill. If the meter moves, and you have ruled out the toilets and the visible fixtures, the leak is likely in a buried or hidden line. That is the point where a professional can help. Hidden leaks often need equipment to locate, and guessing at the location can lead to unnecessary digging or wall openings.

Pay attention to where the water seems to be going. A leak that is clearly coming from a toilet or an outdoor line is a different job from a leak that seems to run under the slab or along a basement wall. Describing the pattern you observed helps a provider decide which equipment to bring and which area to check first.

When to call

Call a provider when the meter moves with all water off, when the toilet test fails and the fix does not solve the problem, or when you cannot find a source but the bill keeps rising. You can reach a local provider who serves your area by calling (708) 221-8167. Have your bill, your meter readings and your notes ready, along with the time and date of each reading.

If the meter has moved during your checks, the leak may be in a buried supply line. Our water line leak detection page explains how providers trace supply lines before any digging begins. If the increase seems linked to a damp floor or a musty smell in the basement, the basement leak detection page covers how to tell a pipe leak from seepage. For a leak you suspect is inside a wall, see the hidden pipe leak detection page.

A short checklist

1. Compare the bill with the last few periods and with the same month last year.
2. Turn off all water and check whether the meter still moves.
3. Run the food coloring test on each toilet.
4. Check under sinks, washing machine hoses, the water heater and each outdoor zone.
5. Record your findings and call (708) 221-8167 if the source is still unclear.