How to Find a Hidden Water Leak in Your DeKalb Home
Before anyone opens a wall or quotes an excavation, you can answer the most important question yourself with a watch and a flashlight. This is the test we run first on every call, and you can do the same version of it in about thirty minutes.
Step one: shut everything off
Turn off every fixture and every appliance that uses water. That means the obvious ones — taps, showers, the dishwasher, the washing machine — and the ones people forget: the refrigerator ice maker, a humidifier on the furnace, a water softener mid-regeneration, an irrigation controller, and any water treatment system with an automatic backwash cycle. Ask everyone in the house to leave the plumbing alone for the duration.
Step two: read the meter
In most DeKalb homes the meter is in the basement near where the service line enters, on the wall facing the street. Some properties have a pit at the curb instead. Find the low-flow indicator — a small triangle, star or dial that spins at very low flow rates. If it is moving at all with everything shut off, you have a leak, and you can stop the test right there.
If it is not moving, note the exact reading including the smallest digits. Then wait.
Step three: wait thirty minutes and read it again
Thirty minutes with no water use. If the reading has changed, water is leaving the system. A very slow leak may need two hours to register, so a no-change result at thirty minutes is encouraging but not conclusive. If you suspect something, run the test overnight — last reading before bed, first reading in the morning, with no water use in between.
Step four: work out whether it is inside or underground
This is the step that saves you the most money, because it decides which trade you are calling.
Find your main shutoff valve — the one where the service line enters the house, usually right after the meter. Close it. Now repeat the reading over thirty minutes.
- The meter still moves with the main closed. The leak is between the city’s curb stop and your house shutoff — in other words, in the buried service line. Nothing inside your house is causing it.
- The meter stops with the main closed. The leak is inside the building, downstream of that valve.
That single piece of information changes the entire approach. Underground means service line locating. Inside means interior leak detection.
Step five: narrow it further inside the house
If the leak is inside, you can keep isolating. Close the cold inlet valve on top of the water heater and repeat. If the meter stops, the leak is on the hot side; if it keeps moving, it is on the cold side. Many homes also have branch valves for an upstairs bathroom, a laundry, or an outside hose bib. Each one you close is another half of the house eliminated.
Check the things that leak without any mystery
Before concluding you have a hidden leak, rule out the obvious silent ones:
- Toilets. Put a few drops of food colouring in the tank, wait twenty minutes without flushing, and look in the bowl. Colour in the bowl means the flapper is passing water — and a bad flapper can waste hundreds of gallons a day without a sound.
- The water softener. A softener stuck in regeneration sends water straight to the drain continuously. Check for constant flow at its drain line.
- Outside hose bibs. A frost-damaged sillcock leaks inside the wall when it is turned on, with nothing visible outdoors.
- The irrigation system. A zone valve that fails to seat sends water into the ground with the controller off.
What your City of DeKalb bill can tell you
Compare the last few billing periods to the same months last year. A household’s usage is fairly stable, so a jump of a few thousand gallons with no lifestyle change is a strong leak signal. Because a hidden leak runs continuously, look especially at whether your minimum usage has risen — that floor is much harder to explain away than a high month.
When to stop testing and call
Call when the meter confirms a leak and your isolation testing has gone as far as valves allow, or straight away if you have any of these: water appearing on a floor, a warm spot on a basement slab, a musty smell that will not clear, a ceiling stain, or a sump pump cycling in dry weather. Those symptoms mean water is already in the structure and the clock matters.
Bring your test results to the call. Telling us “the meter kept moving with the main closed” saves us a step and saves you money on the visit.
Quick answers
It depends entirely on the size of the opening and the pressure behind it, but even a pinhole on a pressurized line can lose thousands of gallons a month. A leaking toilet flapper — which is not hidden but is silent — is commonly the single largest waster in an average home.
You can often narrow it to a zone using isolation valves. Pinpointing a specific location behind drywall or under concrete needs acoustic equipment, thermal imaging or tracer gas. The meter test is genuinely useful homeowner work; the locate is not, and guessing at it is where the expensive mistakes happen.
The test works the same way, you just read it outside. If the lid is heavy or the pit is full of water, call the City of DeKalb Water Division at 815-748-2050 rather than forcing it.
More leak guides
Where DeKalb pipes freeze, how to prevent it, and the first five minutes when one bursts.
Eight causes of a sudden bill spike, ordered from the cheapest fix to the most serious.
Four causes, four different fixes, and how to tell them apart before spending money.
Leak line, answered 24 hours
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