Underground Water Line Leak Detection in Portsmouth, NH
Underground water line leak detection locates a leak on the buried pipe that carries water from the shutoff toward your building. Finding the leak zone first keeps digging focused and helps clarify who is responsible.
Call Portsmouth Leaktrace at (844) 442-1700 if you suspect a buried line leak and want to reach an independent local plumbing provider.
Pinpoint before opening
The location is narrowed down before walls or floors are opened.
Explained before work
Findings and repair options are discussed before work begins.
Two separate jobs
Detection and repair are separate jobs, quoted separately.
Leak-only focus
One problem only: water leaks in and around your home.
What an Underground Water-Line Leak Means
An underground leak is water escaping from a buried, pressurized supply pipe. On most city-water properties, that is the service line running from the street toward the building.
Because the pipe is always under pressure, a buried leak can run day and night. The water may soak into soil, follow the trench or surface somewhere else entirely.
This page covers private, buried supply lines. Indoor concealed leaks, sewer lines and drainage problems are separate issues.
Common Signs Outside the Home
Outside clues are often subtle, especially in sandy or well-drained soil. Look for patterns that persist in dry weather.
- A strip of lawn that stays wet, soft or unusually green.
- Water bubbling or pooling near the curb, walkway or driveway edge.
- A small sinkhole or settling spot along the likely pipe path.
- Ice patches in winter where no runoff should collect.
- Water seeping through the basement wall where the line enters.
One sign alone rarely confirms a buried leak. Several signs along a single line are more telling.
Pressure Changes and Unexplained Water Loss
A buried leak can lower pressure at every fixture, not just one. Showers may weaken when another tap opens, or pressure may slowly decline over weeks.
A water bill that rises with no change in household use is another clue. So is a meter that moves with everything off, when the meter sits after the leak.
Pressure can drop for other reasons, including a partly closed valve, a failing pressure regulator or utility work nearby. Check those before assuming a buried leak.
Wet Ground: Pipe Leak or Drainage?
Wet ground is common after rain and snowmelt. Separating a pipe leak from ordinary drainage starts with the clues in this table.
| Clue | What it suggests | What else may explain it |
|---|---|---|
| Wet strip stays wet in dry weather | Possible buried supply leak | Spring, high groundwater or a buried drain |
| Wet area forms near a downspout | Roof runoff | A leak near the same spot is still possible |
| Water near the curb or sidewalk | Leak near the utility side or shutoff | Stormwater, a neighbor’s line or a street main |
| Greener grass along a straight line | Water following the pipe trench | Fertilizer or soil differences |
| Ground settles over the pipe route | Soil washed away by escaping water | Old trench backfill settling |
| Basement wall wet where the line enters | Leak near the entry or seepage along the pipe | Groundwater entering a foundation gap |
The City of Portsmouth notes that stormwater can cause or aggravate flooding and erosion. Source: City of Portsmouth — Stormwater, reviewed October 2026.
For basement-only symptoms, see how to tell a pipe leak from groundwater.
Where a Private Service Line May Run
Service lines usually run from the shutoff near the street to the point where the line enters the building. The route is often fairly direct, but not always.
Older properties may have lines that bend around trees, foundations or past additions. Some lines were replaced along a new path, leaving the old one in place.
You can often estimate the route by lining up the shutoff, the meter location and the pipe’s entry point in the basement. A professional may confirm it with line-locating tools.
Portsmouth’s Utility-Side and Customer-Side Boundary
The City of Portsmouth describes its service lines as having split ownership. The water system owns the section from the water main to the shutoff valve.
The property owner owns the section from the shutoff valve to the water meter. Source: City of Portsmouth — Water Service Line Inventory, reviewed October 2026.
The City’s November 2025 service-line notice FAQ also describes the curb-stop valve as the dividing point it checks on both sides. Source: City of Portsmouth — Service Line Notice FAQs, November 17, 2025.
Our guide on who owns the water service line in Portsmouth covers the boundary in more detail.
Why the Water Meter May Not Show Every Leak
A meter only measures water that passes through it. Where the meter sits relative to the leak decides whether the leak shows up.
- If the meter is inside the building, a leak on the buried line before it may not register.
- If the meter is near the street, a leak between the meter and the house usually will register.
- A very slow leak may barely move the dial during a short test.
- A leak on the utility side may not show on your meter at all.
So a still meter does not prove the buried line is sound. Our guide explains how to check your water meter for leaks and read the result carefully.
How Underground Lines Can Fail Over Time
Buried pipes fail for many reasons. Some are slow and gradual, while others happen suddenly.
- Corrosion of older metal pipes and fittings.
- Joint or fitting failure where sections connect.
- Ground movement, settling or frost heave stressing the pipe.
- Damage from digging, landscaping or tree roots pressing on the line.
- Older repairs or mixed materials joined together.
The City’s records show some customer-side line materials are still unknown. Material type alone does not prove a leak, but it can inform the assessment.
Freeze and Thaw Risks Without Overgeneralizing
Buried service lines are generally installed with enough soil cover to resist normal freezing. Shallow sections, exposed entry points and areas with little snow cover can still be at risk.
Freeze and thaw cycles can also move soil, which can stress joints. That does not mean every winter leak is freeze damage.
If a buried line stops flowing during a hard freeze, shut off the water if any is escaping and call for help. Do not dig or apply heat to the ground.
Call (844) 442-1700 to talk through outdoor wet spots, pressure loss or a bill that keeps rising.
What Property Owners Can Check Safely
Several checks are safe and need no tools. Do not open utility boxes or operate the curb stop.
Turn off all water use inside, then watch the meter or leak indicator.
Walk the likely line route and note any wet, soft or green areas.
Check whether the wet area changes after a dry day or two.
Look at the basement wall where the line enters for dampness.
Compare recent water bills with the same months last year.
Stay away from open water near the street, which may involve the public main. Report it to the Portsmouth Water Division at (603) 427-1530.
What to Record Before Calling
Good notes help a provider plan the right tools and the right amount of time. Try to record:
- Where the meter is located, inside or outside.
- Where the line enters the building, if you know.
- Photos of wet areas, with something for scale.
- Meter readings with everything off, and the time between them.
- Recent changes, such as landscaping, paving or utility work.
- Any past repairs on the service line.
If you received a City service-line notice, keep it handy. It may describe the material the City has on record.
How Location Work Differs From Excavation
Leak location estimates where the leak is along the buried line. Excavation physically exposes the pipe so it can be repaired.
They are different jobs with different equipment, crews and decisions. Some providers handle both, and some only one.
Location work aims to keep any excavation as small as the situation allows. It cannot guarantee that the first hole will land exactly on the leak.
Acoustic and Correlation Methods: Conditional Tools
Some professionals use listening equipment to hear water escaping a pressurized pipe. Correlation methods compare sound from two points to estimate the leak position.
These tools work best on certain pipe materials and in certain soils. They may be less useful on some plastic pipes or very quiet leaks.
Other methods a professional may use include line locating, pressure testing and tracer methods. Ask the provider which methods suit your line, because availability varies.
Accuracy Limits in Soil and Noisy Locations
Every method has limits outdoors. Ground conditions, background noise and pipe material all affect results.
- Traffic, wind and nearby equipment can mask leak sounds.
- Wet or loose soil can carry sound differently from dense soil.
- Deep or unusual pipe routes make the leak zone harder to narrow.
- Multiple small leaks can blur a single location.
A good finding usually describes a likely zone and a confidence level. Ask what would change the estimate once digging begins.
Detection Versus Line Repair or Replacement
Detection answers where the leak is. Repair or replacement decides what happens to the pipe once it is reached.
| Step | What it does | Who usually handles it | Your decision point |
|---|---|---|---|
| Leak detection | Locates the likely leak zone on the private line | A plumbing provider with location tools | Approve the search |
| Line repair or replacement | Fixes or replaces the private pipe | A qualified plumbing or excavation provider | Choose repair, reroute or replacement |
| Utility notification | Reports a suspected leak on the public side | The water utility | Call before any work near the street |
Once the leak is confirmed, our page on underground water line repair covers the repair choices.
Comparing Spot Repair, Reroute, and Replacement
After location, three repair paths are common. Each depends on the pipe’s condition and the site.
- Spot repair: Fixes a single failed section or joint, best when the rest of the line is sound.
- Reroute: Runs a new line along a different path, useful when the old route is hard to reach.
- Replacement: Replaces the line along its route, often considered for older or repeatedly failing lines.
The provider will explain which options suit your line. That choice belongs to the repair stage, not the detection visit.
Who May Need to Coordinate Utility Shutoff?
Work on a service line may require the water to be shut off at the curb stop. In Portsmouth, that valve is part of the utility’s system.
Property owners should not operate the curb stop themselves. Ask the provider how shutoff and any City coordination will be handled for your job.
The City’s notice FAQ says galvanized-line replacements should use a contractor who coordinates inspections and the curb-stop connection with the Water Division.
Driveways, Landscaping, and Access Questions
What sits on top of the line affects both location and repair. Paving, patios, mature trees and gardens all add access questions.
- Is the line under a driveway, walkway or patio?
- Are there trees or shrubs close to the route?
- Are other buried utilities nearby, such as gas, electric or irrigation?
- Who restores the lawn, paving or plantings after repair?
Before any digging, underground utilities must be marked. Ask the provider how that is arranged.
Cost Factors Without Invented Local Price Ranges
Underground leak detection has no single price. Scope depends on the property and the line.
- Length and depth of the line.
- What covers the line, such as lawn, pavement or landscaping.
- Pipe material and how well it carries sound.
- How many methods are needed to narrow the zone.
- Whether a return visit is needed after initial testing.
Ask how the detection visit is priced and what the findings will include. Repair and restoration are usually quoted separately.
Next Steps After the Leak Area Is Identified
Once the leak zone is marked, plan the next steps in order.
Confirm whether the leak appears to be on the private or public side.
Contact the water utility if the leak may be on its side.
Get repair options and a separate quote for the private-side work.
Arrange utility markings before any excavation.
Plan landscaping or paving restoration after the repair is tested.
Keep the findings and any photos. They help if a second opinion or a later repair is needed.
Other Problems That Mimic Underground Leaks
Several problems look like a buried water leak but are not. Ruling them out avoids unnecessary digging.
- A leaking irrigation line or outdoor faucet.
- A broken drain, sewer lateral or downspout extension.
- High groundwater after heavy rain or snowmelt.
- A neighbor’s leak traveling downhill.
- A public main leak near the street.
A careful assessment checks these possibilities alongside the service line itself.
Frequently Asked Underground-Line Questions
How can I tell if my water service line is leaking?
Look for wet or green strips of lawn, lower pressure and a rising bill with no indoor leaks. A meter test can help, but it may not catch every buried leak.
Who pays to fix a leak on my service line in Portsmouth?
The City says the property owner owns the line from the shutoff valve to the meter. Which side a specific leak is on still has to be determined first.
Does a still meter mean my buried line is fine?
No. If your meter is indoors, a leak on the line before the meter may not register. A still meter only rules out flow through the meter during the test.
Can an underground leak be found without digging?
A professional can often narrow a leak to a zone before digging, which keeps excavation smaller. Some digging is usually needed to reach and repair the pipe.
Should I call the City or a plumber first?
If water is surfacing near the street or the curb stop, contact the Portsmouth Water Division first. If the signs point to your side of the shutoff, a plumbing provider is the usual next call.
Can I turn off the water at the curb stop myself?
No. In Portsmouth, that valve is part of the utility’s system. Use your building’s main shutoff and let the provider coordinate any curb-stop shutoff.
Is underground leak detection the same as repair?
No. Detection locates the leak zone, and repair is a separate job that may involve excavation and restoration. Some providers handle both.
Call (844) 442-1700 to describe your buried-line symptoms and ask about leak location.