Wet Spot in Your Yard That Won't Dry? How to Tell a Water Line Leak From a Sewer Leak or a Sprinkler

A patch of lawn that squishes underfoot in the middle of a Houston August is not the weather. Rain-soaked ground dries out in a few days, but a leaking pipe keeps the soil wet for as long as the pipe keeps leaking. The hard part is that four different things can cause a wet spot, and only one of them is yours to fix with a plumber. This guide walks through how to tell a water service leak from a sewer leak, a sprinkler problem, or a plain drainage issue, using nothing more than your eyes, your nose, and the water meter.

If the spot is growing, sinking, or smells like sewage, call or text (713) 409-7176. The visit to find the source is free, and leak detection is done with listening equipment and a camera rather than a shovel.

The Four Suspects

Every wet spot in a Houston yard comes from one of these:

The water service line. The pressurized pipe from the city meter to the house. Usually 3/4 inch or 1 inch, often buried only 12 to 18 inches deep, and made of PVC, copper, polyethylene, or (in older neighborhoods) galvanized steel.
The sewer line. The gravity drain pipe from the house out to the city tap at the street or alley. Clay, cast iron, or PVC depending on the age of the home.
Irrigation. A sprinkler lateral, a cracked valve, a stuck zone valve, or a leaking backflow assembly.
Drainage or grading. A low corner, a downspout dumping into one spot, a neighbor’s runoff, or a high water table after a wet month.

Diagnosis Table: Read the Clues

Clue	Water service line	Sewer line	Irrigation	Drainage
Where it is	Straight run between the meter box and the house	Over the sewer route from the house (near the cleanout) toward the street or alley	Near a sprinkler head, valve box, or the backflow preventer	Low spot, corner of the lot, under a downspout
Smell	None, clean water	Sewage or rotten-egg odor	None, or chlorine	Musty at worst
Grass	Wet, sometimes yellow from saturation	Noticeably greener and taller than the rest	Lush right at the spot	Normal color, just wet
Timing	Wet all the time, worse as pressure rises overnight	Worse after showers, laundry, and heavy use	Wet after the zone runs, or constantly if a valve is stuck	Dries out between rains
Meter test	Meter moves with everything off	Meter does not move	Meter moves only if the irrigation is on the same meter and the leak is upstream of a closed valve	Meter does not move
Ground	Soft, sometimes a small bubbling or a spring	Soft, may sink or form a dip	Soft only in a small circle	Firm once it dries

Step-by-Step: Narrow It Down in an Afternoon

Map the pipes. Find the water meter box near the curb and the point where the water line enters the house (usually the hose bib closest to the street or the main shutoff). Imagine a straight line between them. Then find your sewer cleanout, usually a capped pipe near the foundation, and imagine the line from there to the street or alley. Note where the wet spot sits relative to both.
Smell it. Kneel down. Sewage has a distinct odor. Clean water from a service line has none. If you smell chlorine, it may be irrigation water sitting in the sun.
Look at the grass. A stripe of thick, dark green grass that follows the sewer route is a classic sewer leak: the soil is being fertilized. Saturated grass over a water line often goes yellow because the roots are drowning.
Run the meter test. Turn off every fixture, the irrigation, the ice maker, and any pool fill. Open the meter box and watch the small sweep hand or the low-flow indicator for ten minutes. Movement means pressurized water is escaping somewhere after the meter. Our guide to a high water bill walks through this test in detail. A sewer leak never moves the meter.
Rule out irrigation. Shut off the irrigation controller and close the valve at the irrigation backflow preventer. Wait 48 hours. If the spot dries, it was a sprinkler lateral or a leaking zone valve.
Check the drainage. If the spot sits in a low corner, under a downspout, or at the property line, watch it through a dry week. Grading problems dry out. Pipes do not.

Why Houston Yards Leak More

Houston sits on expansive clay. In a dry August the soil shrinks and pulls away from pipes; after the first heavy rain it swells back. That movement cracks PVC service lines at fittings, opens joints in clay and cast iron sewer lines, and shears off shallow irrigation laterals. Many service lines here are buried just over a foot deep, so they take the full effect of the shrink-swell cycle and of any truck that drives across the lawn.

Flooding adds a second problem. After a heavy Harris County rain, every yard is wet, and a pipe leak hides in plain sight for weeks. The giveaway is the spot that is still wet after the neighbors’ lawns have dried.

Older neighborhoods with cast iron sewer lines have one more sign to watch for: a dip or small sinkhole along the sewer route. When a cast iron line rusts through at the bottom, water washes soil into the pipe and the ground above it slowly drops. Our guide on cast iron pipes in older Houston homes explains why that happens and what the repair options are.

What a Plumber Does to Confirm It

Acoustic leak detection. For a water service leak, a listening device picks up the hiss of pressurized water escaping underground and pinpoints the spot to within a foot or two, so the dig is a small hole rather than a trench. This is the same equipment used to find hidden leaks under slabs.
Pressure test. Isolating the service line and watching a gauge confirms whether it holds pressure.
Sewer camera inspection. For a suspected sewer leak, a camera run through the cleanout shows the crack, the offset joint, or the root intrusion and measures exactly how far from the house it is. Our sewer camera inspection runs $295 to $350 depending on access, and the recording tells you whether the fix is a spot repair or a longer section.
Hydrostatic test. If the camera cannot see a leak but the symptoms point to the sewer, filling the line and watching the level confirms whether it is losing water.

What Each Fix Involves

Water service line. A pinpointed leak is dug up by hand and repaired with a new section and proper fittings. A line that has failed in more than one place, or an old galvanized line, is replaced from the meter to the house, often by pulling new pipe through a small entry and exit hole rather than trenching the whole yard. Our main water line replacement cost guide explains what drives the price.

Sewer line. A single cracked joint gets a spot repair. A line that is broken, bellied, or rooted along its length is replaced, either by digging or with trenchless pipe bursting or lining, which keeps the driveway and landscaping intact. See the sewer line repair page and the warning signs guide if you are seeing slow drains or gurgling along with the wet spot.

Irrigation. A cracked lateral or stuck valve is an irrigation repair, not a plumbing repair, unless the leak is at the backflow assembly on the house side.

Drainage. Regrading, a French drain, or redirecting a downspout. Not a plumber’s job, but worth confirming before you pay for one.

Who Pays

In Houston the homeowner owns the water service line from the meter to the house and the sewer line from the house out to the city tap at the property line. The city maintains the meter and the mains in the street. If the leak is on the street side of the meter, call 311. If it is on your side, it is yours. Our guide on who is responsible for sewer line repair covers the edge cases, including shared lines and alley taps. Some insurance carriers sell optional service line coverage, which is worth a look if your home is older than 1980.

Why Not to Wait

A water service leak the size of a pencil lead can waste thousands of gallons a month. That shows up on the bill, but the bigger risk is what the water does underground: it washes out the soil under a driveway, a sidewalk, or the edge of a slab, and in clay that means movement and cracks. A sewer leak soaks the yard in wastewater, feeds roots that then grow into the pipe, and can undermine the foundation the same way. Neither one heals on its own.

When to Call

Call Hugo Plumbing when:

The spot stays wet through a dry week, or appears during a drought.
The meter moves with every fixture off.
You smell sewage, or the grass over the sewer route is suddenly lush.
The ground is sinking, bubbling, or there is a visible spring.
Water pressure in the house has dropped, or the bill jumped.
You already shut off the irrigation and it did not help.

The visit to find the leak is free, with no trip charge or diagnostic fee, and the repair is a flat written price before any digging starts. Leak detection is done with listening equipment so the hole is small, and licensed master plumbers (MPL 41319) handle the repair. Larger replacements qualify for financing. Call or text (713) 409-7176, 24/7.

Frequently Asked Questions

How do I know if the wet spot in my yard is a water line or a sewer line?

Start with location and smell. A water service leak sits somewhere on the straight run between the water meter at the street and the point where the pipe enters the house, and the water is clean. A sewer leak sits over the route from the house (often near the cleanout) out to the street or alley tap, and it usually smells like sewage, with grass that grows greener and thicker over the spot. Then do the meter test: with every fixture off, a water leak keeps the meter’s small dial turning, while a sewer leak never moves the meter.

Why is there a wet spot in my yard when it has not rained?

Wet ground during dry weather almost always means a pipe. Drainage and grading problems dry out between rains; a leaking water line, sewer line, or irrigation line keeps the soil saturated no matter the forecast. In Houston, August droughts shrink the clay soil and pull on buried pipes, so leaks often appear in the driest weeks of the year or right after the first big rain shifts the ground back.

Does a sewer line leak make the water meter move?

No. The sewer line is on the drain side of the house, after the meter, and it carries water you have already used. A leaking sewer line does not change the meter reading or the water bill. If the meter is still with everything off and the spot smells like sewage or grows lush grass, suspect the sewer line and have it camera inspected.

Who pays to fix a leaking pipe in the yard in Houston?

The homeowner, in almost every case. The water service line from the meter to the house and the sewer line from the house out to the city tap at the property line or main are the owner’s responsibility. The City of Houston maintains the meter itself and the mains in the street. Some homeowners insurance policies offer optional service line coverage; standard policies usually do not cover the pipe.

Is a wet spot in the yard an emergency?

A water service leak should be handled within days, not weeks: it wastes thousands of gallons, runs up the bill, and can wash out soil under a driveway or slab edge. A sewer leak is a health and foundation issue and should be looked at quickly, especially if the ground is sinking or you can smell it. A sprinkler leak is not urgent but still wastes water. If the spot is spreading, sinking, or bubbling, call the same day.

If your yard won’t dry, call Hugo.