How to Repair an Underground Water Supply Pipe

By
Lee Wallender
Lee Wallender
Lee Wallender

Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.

Learn more about The Spruce's Editorial Process
Updated on 04/07/22
Reviewed by
Richard Epstein
Richard Epstein
Reviewed by Richard Epstein
Richard Epstein is a licensed master plumber with over 40 years experience in residential and commercial plumbing. He specializes in estimating as well as design and engineering for plumbing systems, and he works for one of New York's largest union plumbing construction companies.
Learn more about The Spruce's Review Board
Underground Water Line - Broken

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Project Overview
  • Working Time: 6 - 12 hrs
  • Total Time: 6 - 12 hrs
  • Skill Level: Advanced
  • Estimated Cost: $25 to $100

A cracked or severed underground water supply line is a vexing problem that few homeowners ever want to face. We might be familiar with common indoor plumbing problems, like leaking faucets or wobbly toilets, but when it comes to the hidden underground pipes that deliver fresh water from the city water main to the house, a problem feels much more intimidating. Much like a broken sewer pipe, a broken underground water line usually seems like it will be an expensive, time-consuming project that upsets your entire life. And sometimes it is.

But it doesn't have to be that way. By separating this project into manageable steps, you may be able to repair your underground water supply line by yourself—or at least take on some parts of the work, thus reducing the project's overall cost. Repairing an underground water delivery line is often less arduous than repairing a sewer line since the line is located closer to ground level. Plus, the digging can be done by hand, eliminating the need for hiring an expensive contract excavator.

Before You Begin

Start by determining if you actually have a leak. Some common indicators of a leak in your underground water line include:

  • An unexplained increase in municipal water bills
  • A spinning water meter indicator even though no water in or around the house is turned on
  • Mushy, soft spots in the yard
  • Recessed or swelling ground
  • Low water pressure from faucets or showerheads in the house

If the indicator of a leak is outside, such as recessed ground, make note of where it appears to be the worst. This is where you'll focus your attention.

Warning

Before you do any work, consult with your local permitting office for information about zoning and permits. Check your home's title documents or your county website's tax assessor section for any information about easements that may run through your yard. In some regions, homeowners may be prohibited from doing DIY repairs on the delivery pipes that run from municipal water mains to the house itself.

Safety Considerations

Prior to digging in your yard, you should always have utility lines marked by your local utility location service so you can avoid damaging them when you dig. This service is usually free. A technician will mark your yard with paint indicating blue for potable water lines, red for electrical cables, green for sewer pipes, and orange for gas, oil, and steam. Call 8-1-1 for scheduling.

In regions with cold winters, water lines may be buried quite a distance underground—4 feet or more. Leaving a deep trench exposed poses obvious risks to children and pets, and even adults have been badly injured or killed when the walls of a hand-dug trench collapse on them. Even at 2 or 3 feet deep, a trench that collapses on you when you are kneeling in the bottom to make repairs could lead to a tragic outcome.

Depending on the type of plumbing pipe used for the underground water line, this project could require some decidedly advanced plumbing skills when it comes time to actually replace the damaged section of pipe. You may be faced with cutting and soldering copper pipe with a torch, for example, which is no matter to take lightly when you are dealing with the pipe that brings all fresh water into your home. This is not a repair you want to do a second time because your first effort fails.

What You'll Need

Equipment / Tools

  • Shovel
  • Spade
  • Tarp
  • Hammer
  • Adjustable wrench
  • Screwdriver
  • Dedicated water/gas shut-off tool (optional)
  • Bucket
  • Wet-dry shop vacuum

Materials

  • Plumbing pipes and fittings, as needed
  • Twine or string
  • Wood stakes

Instructions

  1. Locate the Leak

    Once you know the general area of the leak, try to pinpoint its precise location. One way to do this is by running a sightline from your home's street-side water meter to the point where the water supply pipe enters your home. Drive a stake close to the water meter and another stake near the point where potable water enters your home. Run a taut string from stake to stake.

    The damaged underground pipe area will almost certainly lie near the spot where soft, wet ground intersects with this string line. This is where you will begin digging.

  2. Determine Ownership of the Leaking Pipe

    Different communities have different rules for when an underground water pipe problem is the responsibility of the homeowner. Most often, though, the rule is that homeowner holds responsibility for any leak in piping that lies on the house side of the water meter, while the city has responsibility for anything lying on the street side of the meter.

    If you have questions about ownership and responsibility of your leaking underground pipe, a simple call to your community's zoning office can clarify the issue for you.

  3. Turn Off the Water

    Repairing an underground water supply pipe requires that you shut off both the main valve at the home, as well as the water flow from the water main through the delivery line. This isolates the section of underground pipe where the damage is located and prevents possible contamination of water in the home.

    First, shut off the main water shutoff valve inside the home, which is generally located near the point where the water supply pipe enters the home—often in the garage or utility room.

    Next, remove the cover on the recessed water meter box in the yard, and locate the valve beside the meter (on the house side of the meter, not the street side). Carefully turn the valve handle clockwise. It is preferable to use a dedicated water/gas shut-off tool. If you do not have one, you can fit an adjustable wrench over the valve and turn the wrench with a screwdriver inserted into the back of the wrench.

    Tip

    Procedures for shutting off the water delivery pipe can vary. In some communities, the water meter and shutoff valves are separate installations. A separate valve, owned and controlled by the city, governs the water supply pipe running from the water main to the meter. With this configuration, you'll need to call the city utility to have the underground delivery pipe shut off so you can make underground repairs.

  4. Dig the Trench

    Spread out a tarp next to the suspected area of the leak. Your twine or string will indicate the horizontal orientation of the underground pipe; the heaviest concentration of water in the soil provides the vertical axis. Remove the twine and begin digging into the ground. Place the sod and dirt on top of the tarp as you dig.

    Tip

    If you wish to reuse the sod, carefully cut it out with a spade and place it to the side in a separate area.

    Unlike sewer lines, which can run several feet below ground level, water service lines typically are located just below your area's freeze line: from 1 foot to 3 feet below ground—or sometimes more in regions with very cold winters. The depth depends on your region's climate and soil composition, and on the depth of the city water main.

  5. Bail Water From the Trench

    If water continues to gather in the trench, bail it out with a bucket as it collects. As you near the pipe location, you can drain the rest of the water with a wet/dry shop vacuum set to wet mode—or with any kind of portable pump. When leaks are very bad, water removal may need to be handled by a professional.

  6. Expose the Damaged Pipe

    As you near the water water pipe, dig more carefully to expose it fully. Best results are achieved if you dig well below the pipe to provide plenty of access around the pipe—you'll need ample space to cut out and install a new section of pipe.

    Shifting from a shovel to a hand trowel can be helpful during these last stages of digging.

  7. Repair the Water Line

    Depending on the age of your home and any subsequent modifications, your underground water line could be copper, PVC, galvanized steel, CPVC, or PEX. Typically, this pipe will be 1 inch in diameter. Most codes specify that an underground water line should be no less than 3/4-inch in diameter and that it be separated from any waste or sewer lines by no less than 5 feet of undisturbed or compacted soil.

    Cut out the damaged section and replace it with similar materials. Tools and materials required for this work will vary, depending on the type of pipe you have.

    This is the point where you may want to call a professional plumber to make the repair if you are not completely comfortable with your plumbing skills. The professional fee will be much reduced since you have exposed the problem and saved the plumber a considerable amount of labor time.

    Tip

    If you discover that your underground water supply pipe is made of iron or copper, it may be quite old, and future problems are likely as the pipe will continue to corrode. The average life expectancy for underground metal water pipes is 50 to 75 years, and if you live in an older home, it's possible that yours are original and nearing the end of their useful life.

    The prospect of digging up a considerable amount of your yard to replace the entire water supply line is not pleasant, but the reality is that these old underground water lines are living on borrowed time. If underground water pipes are beginning to fail, may be wise to replace the entire line with modern CPVC or PEX, which will be very durable. This, however, is a major project that probably calls for a professional contractor.

  8. Test the Repair

    Once the repair is complete, turn on the water at the meter by turning the nut counter-clockwise. It is not necessary to turn on the water into your house yet. Examine your repair under pressure to make certain that it is secure.

    If you had to take out a work permit for the work, leave the trench open until it is reviewed by an inspector.

  9. Fill the Trench, Flush the System

    When you are satisfied with the repair, fill in the trench with the soil. At the end, replace the sod by hand, if applicable. Turn on the main water valve in the house and run hot and cold water faucets for several minutes to flush out any possible contaminants that may have entered the water pipes during the repair process.

When to Call a Professional

Repairing an underground water line is a time-sensitive project. Until the line is repaired, your home will have either little or no fresh water. If you are not confident about your ability to turn the project around in a satisfactory period of time, you'll need to call in a plumber. Generally, a plumber can fix a single-leak underground water line within a few hours.

Once you've excavated the pipe to expose the problem, it may become clear that your plumbing skills aren't sufficient for the task of actually cutting out and replacing damaged underground water pipes. Don't be averse to calling a plumber immediately if you realize you are in over your head.