Leak detection and slab leak repair
If you're searching for Keene NH plumbers because you hear water running when every fixture is off, or because a spot on the floor has turned unexplainably warm, you're dealing with one of the harder problems in residential plumbing: a leak you can't see. Leak detection and slab leak repair covers finding water escaping from pressurized supply lines or drain piping hidden inside walls, under floors, beneath a concrete slab, or in the buried line between the street and the house — and then repairing it with the least demolition possible. Keene's housing stock makes this especially relevant. A good share of the city's homes near Court Street, Elm Street and the older neighborhoods off Winchester date to the late 1800s and early 1900s, with galvanized steel or soft copper supply lines, cast-iron DWV stacks, and basements that have been finished and refinished over decades. Newer slab-on-grade construction and additions out toward North Swanzey and the Route 9 corridor bring the classic slab leak scenario: copper running in or under concrete, pinholing after years of water chemistry and abrasion. Add Monadnock-region winters — frost depth, unheated crawlspaces, exterior hose bibbs, and seasonal houses drawn down for months — and small leaks have plenty of opportunity to become structural problems. The local, licensed and insured plumbing providers you can reach through this site handle electronic and acoustic detection, pressure isolation testing, and repair options ranging from a spot fix to a full PEX or copper repipe.
What Drives the Cost
Leak detection and slab leak repair is priced in two distinct phases, and understanding that split is the single best thing you can do to avoid surprise. The first phase is diagnosis. A detection visit typically involves isolating the system at the main, watching the meter, pressure-testing hot and cold legs separately, and then using acoustic listening equipment, thermal imaging, or tracer gas to narrow the location. A straightforward single-story home with accessible shutoffs is quick. A house with multiple additions, no isolation valves, a finished basement, and a 1920s layout where nobody knows where the lines actually run takes significantly longer — and that time is the cost. The second phase is access and repair, and this is where the numbers really move. Cutting and patching drywall is modest. Breaking through a 4-inch slab, chasing the line, repairing it, and re-pouring is a different scale of work entirely. A leak under a finished floor — tile, hardwood, or a basement slab under a renovated family room — adds restoration cost that often exceeds the plumbing itself. Exterior service line leaks in Keene bring excavation, and if the line runs under a driveway, mature landscaping, or a stone wall, the restoration question matters as much as the pipe. Other real factors: material choice (a PEX reroute overhead or through walls is frequently cheaper than chasing copper through concrete), pipe depth and frost considerations on buried lines, whether the repair triggers a permit and inspection with the City of Keene, and urgency. After-hours, weekend, and holiday calls carry premium rates. If the leak is contained and you can shut the water off at the main or at an isolation valve, waiting for a scheduled weekday appointment is usually the cheaper path — ask the provider directly whether your situation can safely wait. Always confirm in writing who restores the drywall, concrete, flooring, or landscaping, and whether that's included or a separate trade.
What to Expect
The first conversation is diagnostic triage. Expect to be asked: Is water visible? Can you hear running water with everything off? Is the water meter spinning? Is there a warm spot on the floor, or is the hot water side losing pressure? Is your water heater running more than it should? Those answers determine whether this is a same-day emergency or something that can be scheduled. If water is actively flowing and you can't stop it, you'll be walked through shutting off the main — usually in the basement near where the service line enters, often with a curb stop at the street as backup. Getting the water off immediately limits the damage and often converts an after-hours emergency into a normal-rate appointment the next morning. On arrival, the plumber starts with a full system assessment rather than guessing. That means a meter test, pressure reading at an outside bibb or laundry connection (checking whether your pressure reducing valve is holding a reasonable 50–70 psi), and isolation of the hot and cold legs. Fixtures get ruled out one by one — a leaking toilet flapper or a failed P-trap can mimic a hidden leak and cost nothing to fix. Only after that does electronic detection begin. Once the leak is located, you should get options, not an ultimatum: spot repair at the leak, reroute the affected line through walls or overhead in PEX, or — if the piping is old enough that this is the third pinhole in two years — a partial or full repipe. Each option gets its own price and its own disruption profile. During the actual repair, water to the house is typically off for a few hours for a spot fix, longer for a reroute or repipe, though many providers can restore partial service overnight on multi-day jobs. Afterward, expect a pressure test, a meter recheck to confirm zero flow at rest, and documentation you can give your insurer.
Signs You Need Leak Detection
Hidden leaks announce themselves indirectly. The clearest signal is your water bill. Keene households on city water get a consistent quarterly bill; a jump of 30, 50, or 200 percent with no change in household habits almost always means water is leaving the system somewhere. Confirm it yourself: turn off every fixture and appliance, then watch the water meter's low-flow indicator. If it moves at all, you have a leak. Other symptoms homeowners actually notice: The sound of running water when the house is quiet — often at night, often described as a faint hiss or trickle inside a wall. A warm or hot spot on a basement slab or ground-floor tile, which points specifically to a hot-water slab leak. Loss of hot water pressure while cold stays normal, or the opposite. A water heater that cycles on when nobody has used hot water for hours. Unexplained damp patches on a basement floor that return after you mop them, especially near the perimeter. Musty or earthy odors in a closet, under a stairwell, or along one wall — that smell is the mold conversation, and it's worth taking seriously, because behind-the-wall and under-slab leaks can run for months before anything visible appears. Cupping or buckling hardwood above a crawlspace. Cracking in a slab or a floor that feels soft underfoot. Patches of lawn that stay green and soggy through a dry August, which suggests the buried service line rather than anything inside. Separately, watch for drain-side leaks: staining on a ceiling below a bathroom, a sewer odor near a cleanout or a floor drain whose P-trap has dried out, or gurgling that suggests a compromised DWV stack. Older Keene homes with original cast iron are prime candidates. Any of these justify a detection call. None of them get better by waiting, and the cost of finding a leak is small next to the cost of repairing what a long-running leak does to framing, insulation, and finishes.
Choosing a Provider
Leak detection rewards experience and equipment more than almost any other plumbing task, because the whole value is in opening the smallest possible hole in the right place. Start with credentials. New Hampshire licenses plumbers through the State Board, and you should ask for the license number and confirm the provider carries both general liability and workers' compensation insurance. Liability matters because this work involves cutting into your home's structure; workers' comp matters because someone is working in your crawlspace. Ask whether the person actually performing the detection is licensed, or a subcontractor, and get that clear before scheduling. Then ask about method. A provider who says they'll "start cutting drywall and look" is a different proposition from one who describes isolating the hot and cold legs, pressure-testing, and using acoustic or thermal equipment to localize before any demolition. Ask specifically: what equipment do you use, and what's your typical accuracy radius? Get the pricing structure in writing before work begins. Is the detection a flat fee or hourly? Is it credited toward the repair if you proceed? What are the after-hours and weekend rates, and at what hour do they begin? Is there a diagnostic fee if no leak is found? Ask the restoration question directly. Who closes the hole in the drywall? Who re-pours the concrete? Who reseeds the lawn after excavating the service line? Many plumbing providers handle the plumbing and leave finish work to you or a separate contractor — that's a legitimate arrangement, but you need to know it on day one, not after the floor is open. Finally, ask about options and permits. A good provider will explain when a PEX reroute makes more sense than chasing copper under a slab, will tell you honestly if your piping is past spot-repair, and will handle any permit and inspection required by the City of Keene rather than leaving that to you. A provider who offers only one solution, or who won't quote alternatives, is worth a second opinion.
How do I know if I have a slab leak or just a plumbing problem somewhere else?
The most reliable at-home test is the meter test. Shut off every faucet, toilet, appliance, and ice maker in the house, then look at your water meter's low-flow indicator — the small triangle or dial that spins with even minimal flow. If it's moving, water is escaping somewhere in the system. To narrow it to a slab leak specifically, look for these indicators: a warm or hot spot on a concrete floor or ground-floor tile (a hot-water slab leak heats the concrete above it), the sound of running water that seems to come from the floor rather than a wall, a drop in hot water pressure while cold stays normal, or a water heater that fires up when no one has used hot water. Damp patches that keep returning on a basement slab, or new cracking in the concrete, also point that direction. If the meter spins but you have no slab-level symptoms, the leak is more likely in a wall, a crawlspace, or the buried service line between the street and the house — a soggy green patch in the yard during dry weather is the classic sign of that last one. A licensed plumber can distinguish these in a single visit by isolating the hot and cold legs and pressure-testing them separately, which is far faster and cheaper than exploratory demolition.
Will a hidden leak have caused mold or structural damage, and how would I find out?
It depends almost entirely on how long the leak has been running and where the water has been going. A pinhole leak in copper can release a surprisingly small amount of water per day and still saturate framing, insulation, and subfloor over several months. Under a slab, water often migrates along the path of least resistance and may not surface for a long time; inside a wall, it typically shows up first as a musty or earthy odor, discoloration on drywall near the baseboard, or paint that bubbles in one spot. Once the leak is located and repaired, the plumber can open the affected area enough to expose the wet material, and that's when you can see what you're dealing with. Mold needs moisture plus time — a leak caught within a few days usually dries out with air movement and no remediation. A leak that's been running through a Keene winter in a closed wall cavity or under a finished basement floor is more likely to need a remediation specialist, and a dehumidifier alone won't fix it. Document everything with photos and keep the plumber's written diagnosis: hidden-leak damage is often at least partially covered by homeowners insurance even when the pipe repair itself is not, and the insurer will want a dated professional record of what was found.
How long will my water be shut off during the repair, and should I pay for emergency service or wait?
For a typical spot repair on an accessible line — a pinhole in copper in a basement ceiling or an open crawlspace — water to the house is usually off for roughly two to four hours, including the pressure test afterward. A reroute in PEX through walls or overhead takes longer, often most of a working day, though many providers will restore service at the end of each day on a multi-day job. A slab repair that requires breaking and re-pouring concrete, or an excavation of the exterior service line, can mean water off for a full day or more, and the concrete cure time afterward is separate from the plumbing. Ask for a realistic window when you schedule so you can plan around it. On the emergency question: if you can shut the water off at your main and the leak stops, you can almost always wait for a scheduled weekday appointment and avoid after-hours and weekend premium rates. If water is actively flowing and you cannot stop it, if it's reaching electrical panels or wiring, or if it's running into a finished living space, call immediately — the damage accruing per hour will far exceed the emergency rate. When in doubt, describe the situation on the phone and ask the provider directly whether it can safely wait until morning.
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