# What are the signs of a slab leak? > The signs of a slab leak: a meter that moves with every tap off, a warm spot on the floor, a jump in the water bill, and how to check before you call. URL: https://gracklerepipingaustin.com/guide/slab-leak-signs/ The clearest sign of a slab leak is a water meter that keeps moving with every faucet, toilet and appliance in the house turned off. Other signs are a warm spot on the floor, the sound of running water with nothing on, a water bill that jumps without a reason, and damp flooring or grout. [Grackle Repiping Austin](https://gracklerepipingaustin.com/) offers and manages slab leak reroutes in the Austin area, and this guide explains how to read each sign before anyone opens a floor or a wall. Key takeaways - A meter that moves with everything off is the strongest sign a pressurized line is leaking - A warm patch on the floor points to the hot water line - A sudden jump in the water bill is the first thing some homeowners notice - Signs show that water is escaping, not why; the cause takes testing - Drain leaks under a slab do not move the meter and are a different problem ## The meter check, step by step The meter check tells you whether any pressurized line in the house is losing water. It takes about half an hour. 1. Turn off every fixture and water-using appliance: faucets, showers, toilets (make sure none is refilling), the dishwasher, the washing machine, the ice maker and the irrigation system. 2. Find the meter. In Austin Water’s service area it sits in a ground-level box near the sidewalk, just before the property line. Smart meter lids open with a standard lid key; do not damage the wires on the lid. 3. Look at the dial. Most meters have a small low-flow indicator, a triangle or star, that spins with even a slow leak. Note the reading. 4. Wait 15 to 30 minutes without using any water, then look again. If the indicator moves or the reading changes, water is going somewhere. Next, close the main shutoff at the house (or the customer valve just past the meter, on your side). If the meter stops, the leak is inside the house or under it. If the meter keeps moving with the house shut off, the leak is on the yard line between the meter and the house, which is the work covered by [water line replacement](https://gracklerepipingaustin.com/water-line-replacement/). A leak on the meter or toward the street is Austin Water’s to fix; report it on Austin Water’s leak line, 512-972-1000. A moving meter does not by itself prove a slab leak. A running toilet flapper, a dripping hose bib or an irrigation valve that will not close all move it too. Check those before you assume the worst. ## Signs you can see, hear and feel **A warm or hot spot on the floor.** A leaking hot water line under the slab heats the concrete above it. Bare feet often find it first, on tile or on a slab-on-grade floor in a bathroom or kitchen. A warm patch near the water heater can be normal; a warm patch in the middle of a room that never used to be warm is not. **The sound of water with nothing running.** In a quiet house at night, a leak can make a hiss or a trickling sound near a wall or under a floor. Absence of sound proves nothing. **Damp flooring or grout.** Water forced up through a slab shows as damp carpet pad, darkening grout lines, cupping wood, or a musty smell. Homeowners report water seeping through tile grout as the first visible sign. **Hot water that runs out sooner, or a water heater that runs constantly.** A hot line leak sends heated water into the ground, so the heater keeps working. **Lower pressure at one group of fixtures.** A large leak can drop pressure on the line it is on. Weak flow is a weak sign on its own, though, and the [low water pressure guide](https://gracklerepipingaustin.com/guide/low-water-pressure-austin/) covers the other causes. ## A high water bill can be the first clue Homeowners report a surprise Austin Water bill as the first sign of a hidden leak. A leak on a pressurized line runs every hour of every day, so even a small one adds up across a billing period. If a bill jumps with no change in how you use water, do the meter check before anything else. Keep the bill. If the cause turns out to be a leak, Austin Water’s [Water Leak Bill Adjustment](https://www.austintexas.gov/water/high-water-bill-options) can adjust it when you send the paid repair receipt within 90 days of the repair. The [slab leak reroute cost guide](https://gracklerepipingaustin.com/guide/slab-leak-reroute-cost/) lists what else to keep. ## Hot water slab leak signs Hot and cold lines leak in the same ways, but they show it differently. A hot line leak warms the floor, keeps the water heater running and raises the gas or electric bill along with the water bill. A cold line leak shows mostly at the meter and the water bill, and, if it is big enough, as damp flooring. If you can feel a warm spot, the hot line is the first suspect, and leak detection can confirm it by isolating the hot side at the water heater. ## What causes a slab leak A slab leak is a leak in a water line that runs in or under a concrete foundation. Where a house was plumbed with copper under the slab, as Austin permit descriptions such as “Failed copper pipe inside of slab” show, that pipe can fail in several ways: - **Movement.** Pipe in or under a slab moves when the soil under it moves. Much of central, south and east Austin sits on Houston Black and similar clays that shrink and crack in dry spells and swell when wet, according to the [USDA NRCS](https://soilseries.sc.egov.usda.gov/OSD_Docs/H/HOUSTON_BLACK.html). Pipe can rub against concrete, gravel or a sleeve as it moves. - **Corrosion.** Copper can thin and pit from the inside or the outside. The [copper pinhole leak guide](https://gracklerepipingaustin.com/guide/copper-pinhole-leaks/) explains why there is no single cause. - **Pressure.** High static pressure strains every joint. Austin’s code calls for a regulator where static pressure tops 65 psi, as the [pressure regulator guide](https://gracklerepipingaustin.com/guide/pressure-reducing-valve-austin/) explains. - **Installation and age.** A kink, a nick or a poorly made joint at construction can fail decades later. The [pipe identification guide](https://gracklerepipingaustin.com/guide/what-kind-of-pipes-do-i-have/) helps you work out what is under your floor. No visible sign tells you which of these caused a particular leak. That takes testing, and sometimes it stays uncertain even after the repair. ## Can a slab leak cause foundation problems? It can contribute, but a slab leak does not automatically mean foundation damage, and foundation trouble does not prove a leak. Water from a leaking line wets the soil under the slab. On expansive clay, wet soil swells and dry soil shrinks, so a long-running leak can change how one part of the soil supports the slab. Soil movement can also be what cracked the pipe in the first place. The two can go together without one causing the other. Homeowners report anxiety that each leak signals foundation movement. The useful order is: stop and repair the leak, then, if you see new cracks in walls or floors, doors that stick, or floors that slope, have a foundation professional look. Foundation repair is a separate trade. ## Slab leak or drain leak? The meter check separates them. A supply line is pressurized, so a leak on it runs the meter with everything off. A drain line under the slab only carries water when something drains, so it does not move the meter. Drain leaks show as odors, slow drains, or dampness after showers and laundry, and they are found with a camera and a drain test. They are separate work from a supply leak, as the [guide on drain pipes](https://gracklerepipingaustin.com/guide/does-repiping-include-drain-pipes/) explains. ## What to do once you see the signs If the meter confirms a leak inside the house, shut off the water at the main when you are not using it, so the leak is not running around the clock. Take photos of any damp floor and keep your water bills. Then get the leak located on a specific line, because the fix depends on it. The [repair or reroute guide](https://gracklerepipingaustin.com/guide/slab-leak-repair-or-reroute/) explains how the location, the floor and the pipe decide between a spot repair, a [slab leak reroute](https://gracklerepipingaustin.com/slab-leak-reroute/) and a [whole-house repipe](https://gracklerepipingaustin.com/whole-house-repiping/), and the [slab leak insurance guide](https://gracklerepipingaustin.com/guide/slab-leak-insurance-texas/) covers what to ask your insurer before work starts. ## Questions about this guide ### Can you hear a slab leak? Sometimes. In a quiet house, a pressurized leak under the floor can make a faint hiss or the sound of running water with every tap closed. Not hearing anything proves little, because soil, slab and flooring muffle sound. The meter check is more reliable. ### What happens if you ignore a slab leak? The leak keeps running the meter day and night, so the water bill climbs. Water can work up through flooring, wet the soil under the slab and, on expansive clay, change how that soil behaves. The longer it runs, the more there is to dry out and repair. ### Should I call a plumber or a foundation company first about a slab leak? A plumber first. The first job is to confirm whether water is leaking and from which line, and to stop it. A foundation professional is the right call for cracks, sticking doors or sloping floors, once the plumbing question is answered. ## Related service ### Slab leak reroutes A leaking water line under the slab is confirmed, capped and abandoned, then replaced with a new line run overhead through the attic and down the walls. Details → ## More guides - Decision Guide [Should a slab leak be repaired or rerouted?](https://gracklerepipingaustin.com/guide/slab-leak-repair-or-reroute/)Three ways to fix a leaking water line under a slab, and the conditions that make each one the sensible choice: how many leaks, what the pipe is, what is on the floor and what the attic allows. - Cost Guide [How much does a slab leak reroute cost in Austin?](https://gracklerepipingaustin.com/guide/slab-leak-reroute-cost/)What it typically costs in the Austin area to abandon a leaking line under the slab and run a new one overhead, what the price covers and leaves out, and how it compares with breaking the slab or repiping the whole house. - Decision Guide [Is a slab leak covered by homeowners insurance in Texas?](https://gracklerepipingaustin.com/guide/slab-leak-insurance-texas/)Coverage depends on your policy. This guide explains how a slab leak claim splits into the pipe, the tear-out and the damage, what the Texas Department of Insurance says, and what to have ready before you call your insurer. - Learn [Why is my water pressure low in Austin, and is it the pipes?](https://gracklerepipingaustin.com/guide/low-water-pressure-austin/)Low water pressure in an Austin house can start at the utility, the pressure regulator, the pipe or a single faucet. Two gauge readings, static and flowing, usually tell you which, before anyone talks about repiping. - Learn [What causes a pinhole leak in copper pipe, and when is it time to repipe?](https://gracklerepipingaustin.com/guide/copper-pinhole-leaks/)A pinhole in copper is the last step of a wall slowly thinning from the inside or outside. This guide explains the mechanisms, what they look like, what Austin's water and soil add, and how the leak pattern decides between a repair and a repipe.