Slab Leak vs Water Heater Leak: How to Tell Which It Is
Both can put water on the floor and both can raise your bill. A few simple checks can separate a failing water heater from a leak in the pipes under your slab.
Where to look first
- Check the base of the tank, the pipes and the relief valve for drips or rust
- Look for water pooled directly under the tank
- Check the cold inlet and hot outlet connections
Using the meter
- Turn off all fixtures and appliances.
- Check whether the meter moves. See how to tell if you have a slab leak.
- Close the cold inlet valve to the water heater.
- If the meter stops moving, the leak is on the heater or the hot side of the system.
- If it keeps moving, the leak is elsewhere, possibly on a cold line.
What the results mean
| Result | Likely meaning |
|---|---|
| Water at tank base, meter stops when heater is isolated | Heater or its connections |
| No water at heater, warm floor spot, meter stops when heater is isolated | Hot line leak, possibly under the slab |
| Meter keeps moving after isolating the heater | Cold line or supply line leak |
| Meter still, water present | Not a pressurized leak. Check drains or condensation. See slab leak vs sewer leak. |
Safety
If a gas water heater is involved or you see significant water around electrical components, shut off the power or gas and call a professional. Water heater replacement may require a permit. See Pomona plumbing permits.
Frequently asked questions
Can a water heater leak look like a slab leak?
Yes. Both can raise a bill and wet a floor. The isolation test helps separate them.
What if the heater is fine?
Then the hot line leak may be in the pipes. See slab leak detection.
Should I replace the heater?
That depends on its age and condition. A plumber can inspect it.
Is a warm floor spot from the heater?
A nearby heater can warm a floor slightly. See warm spot on floor.
Keep reading
Need slab leak repair Pomona homeowners can book? See our slab leak repair Pomona page for how we work, or call (909) 415-2610.
Water running, or a warm spot on the floor?
Shut off the main if water is visible, then call. A Pomona plumber will tell you what to do next.
Call (909) 415-2610
