When a homeowner calls us and says "I think I might have a leak somewhere," the conversation goes one of two ways. Either they've already done a few basic checks and can tell us something useful — "the meter is moving with everything off," or "I found water under the bathroom vanity" — or they're calling from a place of complete uncertainty, which is fine, but it means we're starting from zero.
This guide is for the first scenario. There are three things any homeowner can check in about five minutes, without tools, that will tell you whether you have an active leak and give you useful information to describe the problem when you do call. We're not asking you to diagnose the leak — that's our job. We're asking you to gather the information that helps us get to the right answer faster.
In Phoenix specifically, hidden leaks are worth taking seriously. A running slab leak or a slow drip behind a wall can waste hundreds of gallons per day, cause significant structural damage to drywall and framing, and — depending on location — affect your foundation. The sooner you confirm what's happening, the less you're dealing with.
Step One: The Water Meter Test
This is the most reliable way to confirm whether you have an active leak anywhere in the system. It requires nothing more than knowing where your water meter is and being able to read it.
In Phoenix, water meters are typically located at the front of the property, flush with or slightly below the sidewalk or curb in a small rectangular concrete box. Lift the cover (it may have a small notch for a flathead screwdriver or your fingers). Inside you'll see the meter face with a dial and a set of numbers.
This means all faucets, showers, and appliances. Make sure the dishwasher and washing machine are not mid-cycle. Ice makers and refrigerator water dispensers count — if yours has a shutoff behind the fridge, use it. If your irrigation system is on a timer, confirm it won't run during the test window.
Most residential water meters have a small triangular or star-shaped indicator — sometimes red, sometimes silver — that rotates whenever water is flowing. If everything in the house is off and this indicator is moving, you have an active leak. Write down the meter reading (the number displayed), wait 15 minutes without using any water, then read it again. Any increase confirms flow.
If the leak indicator is still and the number doesn't change over 15 minutes, you likely don't have an active supply-side leak right now — though some leaks are intermittent, so a negative result isn't a guarantee.
The meter test catches supply-side leaks — pressurized water lines that are running constantly. It will not catch drain-side leaks (a slow drain pipe drip that only occurs when water is actively running through it) or toilet leaks that only run occasionally. Those require the separate checks below.
What a Moving Meter Means
If the indicator is moving with everything off, you have an active supply leak somewhere between the meter and your fixtures. That could be a pipe under the slab, a line inside a wall, or an exterior irrigation connection. The size of the movement tells you roughly how significant the flow is — a fast-spinning indicator suggests a larger leak; barely-perceptible movement suggests a slow drip or pinhole. Either way, it's worth a call.
If you want to narrow it down further: locate your home's main shutoff valve (usually near the water heater or where the main line enters the house) and close it. Then check the meter again. If the indicator stops, the leak is inside the house or in the lines coming from the meter. If it keeps moving with the main shutoff closed, the leak is between the meter and the shutoff — possibly an irrigation line or exterior spigot.
Step Two: The Sink, Toilet, and Under-Cabinet Check
A large percentage of "hidden" leaks aren't hidden at all once you look in the right places. Spend five minutes doing a quick walk-through of every water source in the house.
Under Every Sink
Open the cabinet under each bathroom and kitchen sink. Look at the supply lines (the flexible tubes running from the shutoff valves up to the faucet) and the drain P-trap (the curved pipe below the drain). Check for:
- Active dripping — obvious, but sometimes slow enough to miss if you're not looking directly at it
- Mineral staining or white crust on fittings — indicates a slow leak that's been evaporating and leaving deposits, possibly for months
- Warped or stained cabinet floor — particleboard swells and darkens when water has been present repeatedly
- Musty or mildew smell inside the cabinet — moisture that's been there long enough to grow mold
In Phoenix, the supply line connections under sinks are worth particular attention. Our hard water causes fittings to corrode faster than in soft-water cities, and the supply lines themselves — especially the older braided steel type — can develop slow weeps at the connection points. These are easy to miss until the cabinet floor is already damaged.
The Toilet Dye Test
Toilets are the most common source of hidden water waste in residential plumbing. A running toilet can waste 200 gallons per day or more — quietly, with no obvious symptoms other than a water bill that's higher than it should be. The flapper valve (the rubber seal at the bottom of the tank that controls water release) degrades over time and develops leaks that are inaudible.
The dye test takes 60 seconds and costs nothing if you have food coloring in the kitchen:
Lift the tank lid and add 8–10 drops of any dark food coloring (blue or red shows clearly). Do not flush. Set a timer for 15 minutes and do not use the toilet during that time.
After 15 minutes, look at the water in the bowl — not the tank. If you see colored water in the bowl without flushing, the flapper is leaking. Water is passing from the tank into the bowl continuously, which means your fill valve is running to compensate, which means you're paying for water that's going straight down the drain.
After the test, flush the toilet to clear the coloring from the bowl and tank. Repeat on every toilet in the house — a home with three bathrooms can have a failed flapper in one toilet that's been running for a year without anyone noticing.
A failed flapper is an inexpensive fix — the part costs a few dollars at any hardware store, and replacement is a 10-minute job for most homeowners. If you're not comfortable with it, we can handle it as part of any service visit. The point is: don't ignore it. A running toilet at Phoenix water rates adds up fast.
Step Three: Read Your Last Two Water Bills
Your water bill is a historical record of consumption, and a spike in usage is often the first indication of a hidden leak — before any visible symptoms appear. Pull up your last two or three bills and compare them.
A meaningful spike is relative to your baseline. If your household normally uses 4,000 gallons per month and last month was 7,000 with no change in habits, that 3,000-gallon difference points strongly to a leak. Phoenix utility bills typically show consumption in CCF (hundred cubic feet) or gallons — if yours shows CCF, 1 CCF equals about 748 gallons, which helps contextualize the numbers.
Keep in mind that seasonal variation is real: outdoor irrigation use goes up dramatically in Phoenix summers. Make sure you're comparing summer to summer or winter to winter rather than across seasons. A spike that tracks with seasonal changes isn't necessarily a leak. A spike in a month where nothing in your habits changed is worth investigating.
What Hidden Leaks Actually Look Like
The term "hidden leak" covers a range of situations. Knowing what to look for in the house itself — beyond the meter and fixtures — helps you catch problems earlier.
Brown or yellow water stains on drywall indicate water has been present and dried repeatedly. The stain is usually not directly below or adjacent to the leak source — water travels along framing and subfloor before dripping, so the visible mark can be several feet from the actual problem.
Paint that bubbles, peels, or looks swollen on a wall or ceiling is a reliable indicator of moisture behind the surface. This is often the first visible symptom of a slow pipe leak inside a wall cavity.
Subfloor that feels soft underfoot — particularly near bathrooms, under kitchen sink areas, or in rooms on a concrete slab — indicates moisture damage to the subfloor or framing. In slab homes, this can also indicate water migrating up from a slab leak below.
Persistent mildew or musty odor in a room, closet, or cabinet — especially one that's on an exterior wall or adjacent to a bathroom — points to moisture that's been present long enough to grow mold. In Phoenix's dry climate, you shouldn't have unexplained musty smells. Take them seriously.
A localized warm or hot area on a tile or concrete floor — especially one that persists when the room is otherwise cool — strongly suggests a hot water slab leak directly below. Run your bare foot slowly across suspect areas in the morning before foot traffic warms the surface.
The T&P (temperature and pressure) relief valve on your water heater has a small discharge pipe running to the floor or exterior. If this pipe is dripping or wet at the outlet, the valve is releasing, which means either the water temperature is set too high or the tank pressure is elevated. This isn't a hidden leak — it's a safety valve doing its job — but it does mean the system needs attention soon.
What to Have Ready When You Call
When you do call a plumber, a few pieces of information will help the conversation move faster and help us give you a more accurate estimate of what you're dealing with:
Did the meter move with everything off? Yes or no, and roughly how fast — barely moving, slow rotation, or spinning quickly.
Is the meter movement inside or outside the main shutoff? If you ran the shutoff test described above, that's useful information that narrows the search area significantly.
Where did you find visible signs? Specific location in the house, what it looks like, and how long it's been there if you know.
What did the dye test show? Which toilet or toilets, and how quickly did color appear in the bowl.
Year the house was built. In Phoenix, this matters — pre-1990s homes have original copper in conditions that make certain leak types more likely. We'll ask this anyway, but having it ready saves time.
Any recent changes? New appliance installation, recent renovation, irrigation work, or anything that involved turning water lines on or off. Sometimes a leak traces directly back to a fitting that wasn't tightened properly during recent work.
None of this is required before you call — if you've confirmed a leak is happening and you don't know anything else, that's enough. But the more of these you can answer, the faster we can help you. Our leak detection service uses acoustic and electronic equipment to locate a leak precisely before any walls or floors get opened. If you've done the checks above and something isn't adding up, call us and we'll walk through it with you.
You don't need tools or plumbing knowledge to confirm a hidden leak. The water meter test, a visual check under your sinks, and the toilet dye test cover the most common scenarios in about five minutes. If the meter is moving with everything off, don't wait — call us. In Phoenix, an active supply leak running undetected is a problem that compounds quickly.