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How to Find an Underground Water Leak Outside Your Home

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So, you suspect that there’s an underground water leak from outside your home…

What now?

That’s every homeowner’s typical response. First off, we’re talking about an underground leak here—literally a place where the sun doesn’t shine. Where do you even begin? Should you dig into the ground yourself to find the source of the leak? How much do you have to pay when you receive the next water bill?

On this page:

While an underground water leak is something you need to take seriously, it’s not something you should lose your head over.

Besides, we got your back.

In this guide, we’ll give you everything you need to know about underground water leaks from outside your home, and how to find them.

How water gets into your home

But before we start, you need to have at least a general idea on how your home’s plumbing system works, specifically how water flows into your home.

It begins with the water main, which is located underground and is connected to your city’s water source. The water main then sends the water to your home through a pipe called the service line or the supply pipe.

Simply put, the service line is the section of the underground pipe that’s within your property boundary. Once the buried line springs a leak, it falls under your jurisdiction to have that pipe fixed.

Dangers of an Underground Leak

Underground leaks are frustrating because they have a way of creeping up on you. Just when you think everything’s fine and dandy, you find a wet spot in your yard.

You’re not just dealing with a wet spot, of course. If you don’t find the source of the leak and patch it up soon, a wet spot on the ground will be the least of your worries.

Here are the potential dangers you’re dealing with when you have an underground leak.

Foundation damage

Once your service line has sprung a leak, there’s no telling where all that water will go. But there’s a strong likelihood that some of it will seep into your home’s foundation. Once it does, water will start to fill your home’s basement, crawlspaces, and tunnels, causing your foundation walls and barriers to sag.

This eventually leads to foundation damage, which can result in a wide range of problems, including sagging flooring, bowed walls, cracks in the foundation wall, warped windows and doors, and more. It goes without saying, but foundation or structural damages can severely devalue your home.


Underground leaks are capable of releasing large amounts of water over a short period of time. Before you know it, you have a spot flood outside your home, causing damage to the pavement, driveway, garden, or even the street outside. You see, water is good at locating weak spots through cracks and crevices, wearing away at the cement or asphalt.

Moisture inside your home

A broken supply pipe or service line not only wreaks havoc on your front yard, but it can also help form puddles inside your home. If not addressed immediately,  it won’t be long until more puddles of water to accumulate on the floor. It gets worse when some of the water enters underneath your sinks, behind walls, and underneath your floors.

Health risks

Wherever there’s water, there’s always a potential for mold growth. Whether it’s inside or outside the household, mold can take root and spread if ignored for a long time.

Worse, regular mold can turn into black mold, which can pose health risks to those who’re exposed to it. Black mold can easily spread through the air as spores, resulting in a wide range of health complications, including frequent sneezing, coughing, skin irritations, headaches, and chronic fatigue. If you want your household to maintain a clean bill of health, fix the leak immediately. More importantly, make your home less inviting to mold by clearing it of moisture.

Property damage

If you think that underground leaks can’t possibly reach your home’s interior, you’re in for a rude surprise. If not immediately addressed, leaks will eventually make contact with walls, flooring, and many other home assets such as carpets, electronic devices, and wooden fixtures.

Noisy pipes

A leaky underground pipe, or any disturbance in the plumbing system, has a tendency to create annoying noises.  If you’re hearing whistling or bubbling noises every time you run a plumbing fixture, that could be a sign that water is gushing from the copper tubing of your service line.

Unpleasant odors

Water leaks often produce unpleasant odors. When water gushes out of the pipe and settles somewhere, it’s likely to produce a musty or moldy smell.

Higher utility bills

Once an underground pipe has sprung a leak, your water meter will continue running. Which is a waste since you’re not able to put the water to good use. The sooner you patch up the underground leak (or any leak for that matter), the better it will be for your finances.

Causes of water line leaks

Now that you know the risks involved in a leaking underground pipe, you might be wondering, what caused the water leak in the first place?

Tough to tell yet. But to help you narrow it down, let’s discuss the many possible causes of water line leaks one by one.

Aging pipes

Supply pipes have an expected shelf-life of 70 years. That’s not to say that you can’t add more years to your service line through proper maintenance, but there will come a time when you have to replace it with a new one. Pipes corrode, get worn out, and lose their structural integrity over time. If your service line is leaking on account of its age, then the only option you have is to have it replaced. Patching it up over and over only for it to spring a leak again every single time will be a waste of your time, energy, and money.

Poor installation

Poorly installed lines are good candidates for leaks. No surprise there. Maybe the fittings were loose, maybe the materials used were substandard. Maybe it’s just incompetence on the contractor’s part. Whatever the reason for the poor installation, it’s on you to hire a contractor who is competent enough to ensure that it won’t happen again.

Pipe corrosion

Pipes get corroded too soon if the water flowing through them contain traces of mineral content or have high acidity. Pipes that are installed under soil with high salinity are also good candidates for premature corrosion. The effect is always gradual. It often starts as a small leak until the corrosion becomes bad enough that causes your service line to burst.

Extremely cold weather

Your pipes will require more attention than the average homeowner if you live in a cooler climate. For one thing, frozen water within pipes expand, causing them to rupture and spring leaks. Frost heaves also cause the soil to swell up from the ground, damaging your water line along with it.

Soil erosion

Soil erosion can put undue pressure on your pipes. If left unchecked for too long, all that pressure will eventually cause your pipes to burst. Subterranean conditions can also cause the soil to shift under the surface, allowing roots to enter and go through the pipes.

How to tell if you have a water leak underground

You should always actively look for signs of a water leak underground. After all, you don’t want to notice the signs until they are painfully obvious. As already mentioned, an underground leak doesn’t become apparent until it has become a serious problem. The earlier you detect the signs, the easier it would be for you to address the issue.

Thankfully, you don’t have to be a professional plumber to confirm if you have a water leak underground.

Here are the steps you can take to detect signs of a water leak.

1. Turn off your home’s shut-off valve

The shut-off valve is the operable part of the service line that comes off the ground. It’s usually located at the home’s front corner. Once you’ve spotted it, shut off the valve by turning the gate valve or the lever handle clockwise.

2. Find the water meter

To check if the water is still flowing towards your home, you only need to check the water meter. To find it, go to your front yard and look for a metal lid on the ground. Raise the lid to see the water meter underneath.

3. Read the meter

See the triangular shaped dial or silver wheel on the water meter? That’s the leak/flow indicator.  As the term suggests, the leak indicator helps you measure your home’s water usage. It’s incredibly sensitive, so much so that it will move even when only a small amount of water passes through it.

Is it moving? If so, then you have a leak in the service line. If not, then the leak is issuing from a pipe inside your home, which is another issue altogether. If the indicator doesn’t seem to be moving but you still suspect that there’s a leak in the service line, do a meter reading and then wait for an hour or two to check if the reading has changed.

If your water meter is digital, you only need to check the flow rate. Is the flow rate higher than zero? In that case, the leak is from the service line.

Underground water leak detection

Once you’ve determined that the leak is coming from the service line, you need to find its exact location.

Here are the places service line leaks often occur:

  • Fittings. Too much pressure within and outside the service line can cause its fittings to crack or come loose.
  • Copper pipe near the shutoff valve. While copper has many advantages over most plumbing materials, contact with mineral deposits and other substances can cause it to corrode. Allow it to corrode further and you’ll soon have pinhole leaks or pipe bursts in your hands.

How to spot a leak

Leak detection is not a guessing game. If you want to spot a leak with the least amount of effort and resources, you have to adopt a more systematic approach. Below are the steps to finding an underground leak in your yard.

The first step is to check for areas where wet spots can be found. The leak is probably located under those wet spots. I say “probably” because there are other variables at play. If your yard is a steep slope, for example, you’re likely to find the leak underneath the top of the slope (water runs downhill, after all).

If the wet spots are too spread out, shut off the valve and wait for at least a couple of days for those spots to dry up. Once the front yard has gotten dry, turn the water back on and check which areas of the yard will show signs of moisture.

Once you’ve marked the areas where the leaks are likely to be found, dig at those areas with a shovel until you find the service line. Dig slowly to ensure that you don’t damage the supply pipe. Also, set the freshly dug soil to one side so you can put them back where they belong if the leak is nowhere to be found.

If you don’t see the leak, dig along the wet areas until you find it. Once it’s been found, shut off the valve and call a plumber.

Acoustic leak detection

I know what you’re thinking: there must be a better way to find an underground leak than digging with a shovel

Well, there is. Lo and behold…  the acoustic leak detection system!

Acoustic leak detection is a leak detection method that uses non-invasive, high-resolution acoustic technology to listen for or detect water sounds from inaccessible locations, including behind walls and under floors. By using such equipment, you can detect leaks without digging or breaking into barrier walls or into the ground.

How does acoustic leak detection work?

Water leaks create a distinct sound when they exit the pipe. As a general rule, small leaks produce high-frequency sounds while large leaks create low-frequency noises. Because an acoustic leak detection device detects leaks through an electronic machine that picks up sound waves, it can provide you with readings that let you distinguish between different water sounds.

According to Underground Surveying, leaks from pressurized water lines make the following sounds:

  • “Hiss” or “Whoosh” from vibrating pipes and pressure reduction
  • “Splashing” or “Babbling Brook” from water flowing along or around the pipe
  • Fast “beating/thumping” sounds from jets of water hitting the underground cavity wall
  • “Clinking” sounds of stones and pebbles falling and bouncing on the pipe

For a more in-depth explanation on how to detect leaks using an acoustic leak detection system, visit Underground Surveying’s comprehensive guide.

How much does it cost to repair an underground water pipe?

Now let’s get to the nitty-gritty: How much would it cost to stop your underground water pipe from leaking? Well, that will depend on several factors, which are:

  • Length of the supply pipe or service line
  • Severity of the damage
  • Location of the pipe
  • Plumber’s rates and fees

Cost to repair leaking pipes

The number of repair costs will depend on the severity and nature of the plumbing issue. If we’re dealing with a pinhole leak, then we’re talking around $150. It also depends on the pipe’s location. If it’s difficult to access, prepare to spend up to $500, just to be on the safe side.

Cost to repair burst pipes

Burst pipes, as the term implies, have bigger damages, causing voluminous amounts of water to escape from the service line. Pipes often burst during winter months because frozen water has a tendency to expand, resulting in breaks or big gaps in the pipe. To fix burst pipes, prepare to spend between $400 and $1,200. Again, the location plays a big factor here, so the aforementioned range should help you make at least a rough estimate of the total repair costs.

Flat rate or hourly rate?

Plumbing issues vary in complexity, but it can be tough to judge a plumbing issue’s complexity if you’re still in the early stages of a project. This makes pricing very tricky, making it difficult for a contractor and a homeowner to come to a mutual agreement.

To arrive at a deal that protects the interests of both parties, you and the contractor need to decide on a pricing model: flat rate or hourly rate?

Some homeowners don’t mind paying contractors an hourly rate because paying by the hour only seems straightforward and fair. The drawback in this pricing model is that repair costs become more expensive the longer it takes for a project to finish. This is why you need to make sure that the project’s scope is well defined and validated before you agree to an hourly contract. Because let’s face it: there are contractors out there who’d voluntarily stall the project in order to squeeze more money from you.

If you don’t like surprises, a flat rate contract is more ideal for you. In this pricing model, you only have to pay the amount you and the plumbing contractor have already agreed to before the project even started. No matter how long it takes for the contractor to complete the project, you’ll still be paying the same amount. There may be times when a contractor may want to increase the price. Before you agree to pay an additional amount, make sure that the contractor makes it clear to you why the overall price had to be increased. Make sure that the contractor puts it in writing.

Who do you call if you have a water leak in your yard?

If the leak is in the water service line (the line connecting your home to the water main), then the problem is your responsibility.  In such cases, calling a professional plumber is the most logical choice.

But if the water leak is issuing from a section of the pipe that’s outside the service line, call your local water service provider to request for someone to address the water leak.

Getting quotes from a pro

An underground leak can be a real pain in the neck, so we hope that this comprehensive guide has proven to be helpful to you. If you’re still having leakage issues and you’re at your wit’s end on what to do next, it’s in your best interests to hire a professional plumber.

But here lies another challenge: where and how do you find a contractor who can address your needs?

We’d be happy to help you with that, too.

While there are many competent and trustworthy contractors out there, there’s always the possibility that you’ll end up hiring someone who’s not only fit for the job but who have no qualms about screwing you over (knock on wood). It can be extremely difficult to keep track of all the expenses involved in a water leakage repair job, and you need someone whom you can trust with your hard-earned money.

If you’d allow me to give you some advice, it is this: get as many quotes as you can from competing contractors! Also, special emphasis on the word “competing” there. After all, contractors are more likely to put their best foot forward if they know there’s competition.

Granted, looking for competent contractors requires effort. You need to put in the time to scour the web for reviews and ask around for referrals to get quotes that are worth your time.

But what if I tell you that you can skip all that and still be able to receive up to four FREE quotes from competing contractors in no time?

All you need to do is fill out our form! Once submitted, contractors that match your criteria will contact you themselves and send you their quotes for free. And don’t worry, for there’s no commitment involved here. If none of the offers fit what you’re looking for, then that’s alright, too. You’re well within your right to ignore them. The important thing is that you’ve taken the first big step towards finding a contractor who can finally put a stop to your underground leak woes.

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