How do I find a hidden water leak? (The meter test, the warning signs, and what a plumber actually does)

A water bill that jumps for no reason is your house filing a report: something is moving water, you just can't see where. And in Louisville that leak stings twice, because MSD figures your sewer charge from the same meter reading, so every hidden gallon shows up on both halves of the bill. The good news is you can usually narrow a hidden leak way down yourself, for free, in about ten minutes. Here's how we'd do it at our own houses, the warning signs worth trusting, and what we actually do when the free checks don't find it.

The meter test: ten minutes, no tools

Your water meter is the one honest witness in this whole story. Every drop that enters the house passes through it, and it can't be fooled by a leak being out of sight. In most Louisville homes the meter sits in a covered pit near the sidewalk or the property line. Lift the lid carefully (a flathead screwdriver helps, and yes, sometimes there are spiders on duty) and you'll find the register: a numbered readout plus a small low-flow indicator, usually a little triangle, star, or gear that spins when even a trickle moves through the line.

• Shut everything off Every faucet, the ice maker, the washer, the dishwasher, any irrigation, and nobody flushes while the test runs. You want the house asking for exactly zero water.
• Watch the low-flow indicator With everything off, that little dial should be dead still. Give it a full minute, a slow leak turns it slowly. If it's moving, water is leaving the system somewhere. If it's genuinely still, you likely don't have an active leak at all, and the bill spike deserves a different explanation.
• Close your main shutoff and look again This is the part most people skip, and it's the best trick in the whole test. Your home's main valve is usually where the water line comes through the basement or crawl space wall. Close it, then walk back out to the meter. Still moving: the leak is in the buried service line between the meter and your foundation. Stopped: the leak is inside the house, downstream of that valve. In two minutes you've cut the search area in half.
• No indicator on your meter? Run it overnight Some registers don't have a low-flow dial. Write down the exact reading before bed, use no water overnight, and read it again in the morning. Any change after eight hours of zero use is your answer.

The warning signs of a leak you can't see

The meter tells you that water is escaping. These tell you where to start looking. No single one proves anything on its own, but two or three pointing the same direction usually aren't a coincidence.

• The bill jumped with no change in habits Compare against the same month last year, not last month, because summer watering makes a normal fall bill look like a leak. If usage is up against the same season with the same routine, believe it.
• You hear water moving with everything off In a quiet house with everything off, a faint hiss or trickle near the walls where pipes run is water going somewhere it shouldn't.
• A warm patch on the floor If a hot line under a concrete slab is leaking, the floor above it warms up, and pets will find that spot before you do. A lot of mid-century Louisville ranches sit on slabs with the water lines run underneath.
• Stains, bubbling paint, or soft drywall A pressurized pinhole doesn't drip politely, it mists inside the wall or ceiling cavity until the paint bubbles or the drywall goes soft. Ceilings under second-floor bathrooms are the classic spot to check.
• The water heater runs when nobody's used hot water A leak on the hot side quietly drains heated water, so the heater keeps cycling to warm the replacement. If you hear it firing at odd hours in an empty house, ask why.
• One lush green stripe in the yard A soggy spot that never dries, or a strip of grass noticeably greener than the rest running between the meter and the house, is the buried service line watering your lawn for you.

What a plumber actually does to find it

If the free checks come up empty and the meter still says water's moving, this is where we come in. A standard diagnostic visit runs $89. We rerun the meter and shutoff isolation the same way you did, then go further: pressure testing to confirm the system won't hold, isolating the hot side from the cold side to learn which one is bleeding, and checking the concealed offenders room by room. When the evidence points underground, we bring listening equipment. Sound-sensing leak detection runs $400–$500, and its whole job is to pinpoint the leak so any digging stays small and targeted instead of trench-first, ask-questions-later. On older properties where nobody knows where the line even runs, tracing a buried metallic water line is its own task at $300–$400. From there you get real options with real numbers: a targeted spot repair on a buried service line starts around $2,000–$2,200, a leak inside a wall is usually a small access-and-repair job, and a leak under the slab has its own playbook we've written about separately. The point of the detection step is simple: you decide with facts instead of guessing with a jackhammer. If you want a ballpark before anyone comes out, Ask Goldie can walk you through it.

Common questions we get