Leak Detection in McLean, VA
Hidden water leak? We pinpoint it with listening equipment, thermal cameras and pressure tests before we open anything, then fix it on the same visit when we can.
- Non-invasive methods first
- Walls, ceilings, floors & yards
- Open 24/7
A hidden leak rarely shows up where it starts. Water runs along pipes, joists and concrete before it stains a ceiling or soaks a carpet. That is why cutting into a wall where the stain appears often misses the source. Professional leak detection finds the actual failure first, so the repair is a small patch rather than a renovation. We handle the detection and the plumbing repair on the same call whenever we can.
What our leak detection service includes
- A water meter test to confirm whether water is leaving the system.
- Pressure tests that isolate hot, cold, supply and irrigation lines.
- Acoustic listening on walls, floors and the ground over buried pipes.
- Infrared thermal imaging to spot warm or cool wet patches.
- Moisture meter readings to map how far water has spread.
- Tracer gas testing for lines that are too quiet for acoustic tools.
- Toilet, faucet, water heater and fixture checks for the common "silent" leaks.
Signs you have a hidden leak
| Sign | Where you notice it | Why it matters |
|---|---|---|
| Water bill rising with no change in use | Fairfax Water or Town of Vienna bill | Water is escaping somewhere on your side of the meter |
| Meter leak indicator moving with taps off | Meter box near the street or meter inside | Confirms an active leak |
| Sound of running water when nothing is on | Walls, basement, under floors | A pressurized line is leaking |
| Warm spot on the floor | Basement slab, tile, wood | Often a hot-water line leak under the floor |
| Stain, bubbling paint or sagging drywall | Ceilings under bathrooms, walls by plumbing | Water has been collecting for some time |
| Musty smell or mold | Closets, basements, cabinets | Slow leak feeding moisture into materials |
| Soggy or extra-green lawn strip | Between the street and the house | Possible service line leak |
| Low water pressure | Several fixtures at once | Water may be leaving before it reaches you |
How we find a leak, step by step
- Interview and walk-through. We ask when you first noticed the problem and look at the meter, water heater, fixtures and visible pipes.
- Meter test. With every fixture off, we watch the meter and its leak indicator. Movement confirms a leak on the house side of the meter.
- Isolate the line. Pressure tests on separate sections tell us whether the leak is on the hot side, cold side, irrigation, pool fill or service line.
- Pinpoint. Acoustic microphones pick up the sound of water escaping a pressurized pipe. Thermal cameras show temperature changes. Moisture readings confirm the wet zone.
- Mark and explain. We mark the spot, show you the readings and explain repair options and their cost.
- Repair and retest. After the repair we pressure test again and recheck the meter so you know the leak is gone.
Leak detection methods compared
We pick the method for the pipe and what surrounds it.
| Method | What it detects | Best for | Limits |
|---|---|---|---|
| Meter test | Any flow with fixtures off | Confirming a leak exists | Does not show where it is |
| Pressure test | Pressure drop in an isolated section | Narrowing to one line | Needs sections that can be isolated |
| Acoustic listening | Sound of water escaping under pressure | Slabs, walls, buried lines | Noisy rooms and very small drips are harder |
| Thermal imaging | Temperature differences | Hot-water leaks, wet ceilings and walls | Shows symptoms, not always the exact source |
| Moisture meter | Water in drywall, wood, concrete | Mapping damage | Confirms wetness, not pipe location |
| Tracer gas | Gas escaping from a drained line | Quiet or plastic lines, long yard runs | Line must be drained and charged |
| Camera inspection | Cracks, roots and breaks inside drains | Drain and sewer leaks | Not used on pressurized supply lines |
Common causes of leaks in McLean homes
Many McLean houses were built in the 1950s and 1960s. Older galvanized steel pipe rusts from the inside out. Copper from the same era can develop pinhole leaks, which we cover in our repiping service. Newer homes have long pipe runs, many fixtures and irrigation lines that give leaks more places to hide.
Other causes we see often:
- Worn toilet flappers and fill valves. The EPA says a worn flapper can leak thousands of gallons a year without a sound.
- Failed fittings behind showers and vanities.
- Water heater tanks, valves and connections.
- Freeze damage to pipes on outside walls and hose bibs after a cold snap.
- Shifting soil and roots around the buried water line.
- Fixture supply hoses under sinks, washers and refrigerators.
What affects the cost of leak detection
We quote after we understand your home, not from a price list. The main factors are:
- How many lines must be isolated and tested.
- Whether the leak is in a wall, under a slab, in the yard or in a pool.
- Floor and wall materials over the pipe.
- Whether tracer gas or extra equipment is needed.
- Whether the repair is done on the same visit.
- Night, weekend and holiday timing.
Our guide to leak detection cost explains each factor and how to compare quotes.
DIY checks vs calling a plumber
You can safely do a few checks yourself before you call:
- Turn off every fixture and watch the meter for two hours. The EPA uses the same test.
- Put food coloring in each toilet tank. Color in the bowl within 10 minutes means a leaking flapper.
- Look under sinks, behind the washer and around the water heater for drips.
Call a plumber when the meter moves with everything off, when you see stains or hear water, or when a floor feels warm. Do not cut into walls to search. It rarely finds the source and adds repair work.
Insurance and permits in Virginia
Virginia's Bureau of Insurance consumer guide tells homeowners to give immediate notice of a possible claim, protect the property from further damage and keep records of emergency repairs. Coverage for the leak itself, the damage it caused and the cost of finding it varies by policy, so check yours with your agent.
Fairfax County requires a residential plumbing permit to replace or repair plumbing equipment and fixtures. If your repair needs one, we tell you before work starts.
Local note
Leak patterns change across our service area. In Great Falls, long service lines and private wells mean leaks can hide far from the house. In Tysons, condo leaks often show up in the unit below. Older homes in Falls Church and North Arlington are more likely to have galvanized or aging copper pipe.
Leak detection questions
How do professionals find a hidden water leak?
We confirm a leak with a meter test, isolate the leaking line with pressure tests, then pinpoint it with acoustic listening, thermal imaging, moisture readings or tracer gas. Combining methods narrows most leaks to a small area before anything is opened.
Will leak detection damage my walls or floors?
Detection itself is non-invasive. The tools work through drywall, tile, wood and concrete. We only open a surface once we know the leak is behind it, and we keep that opening as small as the repair allows.
How long does leak detection take?
Many homes take one to three hours. Long pipe runs, several bathrooms, irrigation, pools or leaks under a slab can take longer. We tell you what we are testing and why as we go.
Can you find a leak in the yard?
Yes. Leaks in the buried service line between the meter and the house are common. We trace the line, listen along it and mark the leak so the repair needs a small hole instead of a long trench.
Can you fix the leak after you find it?
Yes. We are a full plumbing company, so we can repair the pipe, fitting, fixture or line we find. Larger repairs such as a reroute or new water line may be scheduled as a separate visit.
Does homeowners insurance pay for leak detection?
Coverage depends on your policy. Virginia's Bureau of Insurance tells policyholders to give immediate notice of a possible claim and protect the property from further damage. Call your agent and keep our findings and photos for the claim.
Sources
- U.S. EPA WaterSense — Fix a Leak Week
- Fairfax County Land Development Services — Residential Plumbing Permit
- Fairfax Water — Your Plumbing (archived page)
- Virginia State Corporation Commission, Bureau of Insurance — Homeowners Insurance Consumer's Guide
Last reviewed 2026-11-07. This page is general information, not legal or insurance advice. Read how we research and check pages in our editorial policy.
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Think you have a hidden leak? Call for leak detection in McLean.
Call McLean Plumber Works any time, day or night. A plumber picks up and talks you through next steps.