If a plumber has ever told you the problem is “in your lateral” or “on the pressure side,” and you nodded politely without knowing what that meant, you’re in good company. Most homeowners have no idea how water actually gets from the street into their house, or which parts of that journey they’re responsible for paying to fix.
It matters more than you’d think. Knowing which line is leaking can be the difference between a repair the water utility handles and a bill that lands squarely on you. Here’s the plain-English version.
The city main: the utility’s pipe
The water main is the large pipe running under your street, serving your whole neighborhood. It belongs to the water utility, and if it breaks, that’s their crew and their budget. You’ll usually know a main break when you see one, because it tends to announce itself dramatically, with water coming up through the pavement.
The meter: where responsibility usually changes hands
Your water meter is the dividing line, both literally and financially. As a general rule across most California municipalities, the utility owns everything up to and including the meter, and the property owner owns everything from the meter to the house. That’s the standard arrangement, but the details vary by city and by whether we’re talking about water or sewer, so it’s always worth confirming with your provider. In Santa Rosa, you can check with the City of Santa Rosa Water & Sewer department. Sewer laterals follow their own rules, which Sonoma Water explains here.
Your meter is also the best leak-detection tool you already own. Turn off every faucet and water-using appliance in the house, then watch the meter. If it’s still creeping, water is going somewhere it shouldn’t.
The service line, or lateral: your pipe, and the usual suspect
The service line, often called the lateral, is the pipe that runs from your meter to your house. It’s typically buried a few feet down and may run under your lawn, your landscaping, your driveway, or your patio.
This is where we find a large share of the hidden leaks we’re called out for, and it’s the one that surprises people most, because it’s almost always the homeowner’s responsibility. Older Sonoma County homes often have galvanized steel or early copper service lines that have been in the ground for decades. Add our shifting clay soils and tree roots, and pinhole leaks and joint failures are just a matter of time.
A leaking service line rarely announces itself. Because it’s buried, the water quietly saturates the soil, and the first thing most people notice is a water bill that jumped for no reason, or a patch of lawn that’s suspiciously green. We cover the full list of warning signs in 5 signs of a hidden water leak.
One word, two meanings: water lateral vs. sewer lateral
Here’s where a lot of homeowners get tripped up. “Lateral” gets used for two completely different pipes, and mixing them up can cost you.
Your water service lateral is the pressurized pipe bringing clean water from the meter into your house. Your sewer lateral is the gravity-fed pipe carrying wastewater from your house out to the city sewer main. Different direction, different pressure, different failure symptoms, and sometimes different rules about who’s responsible.
In Santa Rosa, city code puts the sewer lateral squarely on the property owner, who is responsible for maintaining it from the city sewer main to the structure. The city may, at its own discretion, handle occasional repairs on the short stretch between the main and the back of the curb or sidewalk, but that’s their option rather than your entitlement. Sonoma Water has a good overview of private sewer laterals if you want the details.
The practical difference: a leaking water lateral shows up as a rising bill and wet ground, because it’s under constant pressure. A failing sewer lateral shows up as slow drains, backups, or odor, because it only carries water when something drains.
Pressure lines: why a small leak is never small
“Pressure side” or “supply side” refers to any line carrying pressurized water into or through your home, as opposed to drain lines, which rely on gravity. Everything from the main to your faucets is under constant pressure.
That’s why a hidden supply leak is so costly. It doesn’t only leak when you’re using water, it leaks continuously, day and night, for as long as it takes you to find it. The U.S. EPA estimates household leaks waste nearly one trillion gallons nationwide every year, with the average home losing more than 9,300 gallons.
Drain lines fail differently. They aren’t pressurized, so they leak only when something drains, which usually shows up as staining on a ceiling below a bathroom or a musty smell under a sink.
Lines inside and under the house
Once water reaches your home, it branches out to fixtures and appliances. In houses built on a concrete foundation, those pipes may run beneath the slab. When one of those fails, it’s a slab leak, and it can quietly undermine your foundation before you see a drop of water. Warm spots on the floor and the sound of running water with everything shut off are the classic clues.
Irrigation lines: the ones nobody thinks about
If your property has sprinklers or drip, you have a whole second network of water lines out there, and in Sonoma County that network is often larger than the plumbing inside the house. On bigger lots, vineyards, and mature landscaping, it can run for hundreds of feet.
Irrigation lines behave differently from the rest of your plumbing in a few ways that matter:
They’re shallow. Most irrigation is buried only a few inches to a foot down, which makes it vulnerable to shovels, aerators, gopher activity, root movement, and simple age. PVC and poly tubing also become brittle after years of sun exposure at exposed points.
They usually branch off the house, with their own shutoff. In most homes the irrigation system taps off the house plumbing rather than the buried service line, and it has a dedicated shutoff valve, often paired with a backflow preventer to keep landscape water from flowing back into your drinking water.
That dedicated shutoff is genuinely useful, and not just for winterizing. It means the irrigation system can be isolated and tested completely separately from the house, which is often the fastest way to figure out whether a mystery leak is out in the landscaping or somewhere in your plumbing. It’s worth knowing where yours is before you need it.
They only leak part of the time. Unlike a pressurized service line running 24/7, many irrigation leaks only lose water when a zone is actually running. That makes them sneaky. The loss hides inside what looks like normal watering, and because it’s soaking into soil that’s supposed to be wet, nothing looks wrong on the surface.
They waste an enormous amount of water. The EPA estimates that an irrigation system with a leak roughly the width of a dime can waste about 6,300 gallons a month. On a summer bill in Sonoma County, that adds up fast.
Signs your irrigation is the culprit
Look for a zone that never seems to dry out, an area that’s greener or growing faster than everything around it, soggy ground or pooling after a cycle finishes, sunken or eroded soil along a line’s path, sprinkler heads that weep between cycles, or a noticeable pressure drop so heads that used to throw water across the lawn now dribble.
A quick way to narrow it down yourself: shut off the valve to the irrigation system only, leaving the house on, then check the meter. If the meter stops moving, the leak is on the irrigation side. If it keeps creeping, the problem is somewhere in the house or the service line.
How we figure out which line is leaking
You don’t have to guess, and you definitely don’t have to start digging. We isolate sections of the system and pressure test them to narrow down where the loss is happening, then use acoustic listening equipment, line locating, and sometimes dye testing to pinpoint the exact spot. Once we know precisely where the leak is, we open one small access point and repair it, instead of trenching your yard hoping to get lucky.
If you’d rather never have this problem again, a smart water monitoring system watches your flow around the clock and can shut the water off automatically when something goes wrong.
Not sure which line is leaking?
That’s what we do. Hometown Leak Detection is a family-owned company serving Sonoma, Marin, and Napa, with 160+ five-star reviews and over 20 years of experience. We find it without tearing up your property, and we fix it.
Frequently asked questions
Who pays to repair a leaking water service line?
In most cases the property owner does, because the service line from the meter to the house is generally the homeowner’s responsibility. The utility typically covers the main and the meter itself. Rules vary by city, so confirm with your local water provider.
What’s the difference between a lateral and a main?
The main is the utility’s large pipe running under the street and serving many homes. The lateral, or service line, is the smaller pipe that branches off and serves your property alone.
How do I know if my irrigation system is leaking?
Shut off the valve to the irrigation system only, leaving water on in the house, then watch your meter. If it stops moving, the leak is on the irrigation side. Also look for a zone that stays soggy, an area that’s greener than the rest of the yard, or sprinkler heads that dribble instead of spraying, which often points to a pressure loss somewhere in the line.
Is a sewer lateral the same as a water lateral?
No. The water lateral is the pressurized line bringing clean water from the meter to your house. The sewer lateral is the gravity-fed line carrying wastewater from the house to the city main. They fail differently and the responsibility rules aren’t always identical, so it’s worth knowing which one you’re dealing with.
Does homeowners insurance cover a service line leak?
It depends on your policy. Many standard policies cover resulting water damage but not the pipe repair itself, and some insurers offer service line coverage as an add-on. Check with your agent, ideally before you need it.
Can you find a buried leak without digging up my yard?
Yes. That’s the entire point of professional leak detection. Using pressure testing, acoustic equipment, and line locating, we pinpoint the leak first and then open only the small area needed to repair it.
Hometown Leak Detection Inc. · Licensed & insured · CSLB Lic. #1076501 · Serving Sonoma, Marin & Napa · (707) 890-0904
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