Quick answer: A water leak test uses a pressure gauge on an outside faucet to check a home’s water system for hidden leaks. The plumber records the city water pressure (typically 60–80 PSI), shuts the water off at the meter, and waits 15 minutes. If the pressure holds, the system is tight. If the pressure drops, there is a leak somewhere between the meter and the fixtures. The test takes about 20 minutes and requires no digging, no cutting, and no damage to the home.
That’s the whole concept. Below is exactly how I run this test on a real house — the same procedure we filmed, step by step.
I’m Roger Wakefield, a Texas Master Plumber with 45 years in the trade. In the video below, I run this exact test on a real home — a pre-purchase inspection where a buyer wanted to know if the house had hidden leaks before closing. Spoiler: it did, and the test caught it. At LeakPro, this pressure test is the first thing we teach, because it’s the first thing you do on every residential leak call: before you hunt for a leak, prove there IS one.
No — and this trips up a lot of people. A hydrostatic test pumps the system up to raise the pressure higher than normal, usually to test the sewer or drain system. A water leak test does the opposite of adding pressure: it simply watches whether the home’s existing city water pressure holds when the supply is shut off.
Think of it this way: a water leak test asks “is this system losing water right now?” A hydrostatic test asks “can this system hold pressure beyond normal conditions?” On a residential leak call — especially a suspected slab leak — you start with the water leak test, because you need to answer two separate questions: does the water system leak, and does the sewer system leak. This test answers the first one.
Here’s the exact procedure from the video:
On the house in the video, we lost about 10 PSI in roughly 16 minutes. That’s not ambiguous — that’s a leak. A tight system holds its pressure essentially flat for 15 minutes.
If the test shows a leak, the next question is where: in the yard between the meter and the house, or under the house itself? If the home has a shutoff valve at the house, close it and re-test — pressure that holds with the house valve closed means the leak is in the yard line; pressure that still drops means it’s in the house. No valve at the house? That’s worth installing, because it lets you isolate yard from house on every future test. From there, professional listening equipment pinpoints the exact spot so you open one hole instead of five.
One thing you must not forget, and I say this from experience: turn the water back on at the meter before you leave. The homeowner will remember you forever if you don’t — for the wrong reason.
The house in the video was a real estate deal — a buyer testing before purchase (and note: this was a pier and beam home, not a slab, which proves the test works on any foundation type). When the test confirmed a leak, the decision went back to the buyer and seller: the seller can repair it before closing, or the buyer can negotiate money off the price and handle the repair on their own schedule. Either way, the buyer avoided inheriting a hidden leak — a 20-minute test that can save a homebuyer thousands.
For homeowners not buying or selling: a confirmed leak means it’s time for professional leak detection to pinpoint the location. High water bills, the sound of running water, or a water meter that spins with everything off are the classic signs that this test is worth running.
A water leak test is the fastest, cheapest, most reliable first step in residential leak detection: gauge on, read the pressure, water off at the meter, wait 15 minutes, read again. Pressure drop = leak. It’s the exact test professional plumbers run first on every suspected slab leak — and it’s the first skill we teach in our hands-on training. If you’re a plumber who wants to turn tests like this into a profitable leak detection service, call us at 888-853-2577.
If a plumber performs it, a water leak test is often part of a standard leak detection service call. The equipment itself is minimal — a pressure gauge that threads onto a hose bib costs $10–$20 at any hardware store, which means handy homeowners can run the basic version themselves before ever calling a pro.
About 20 minutes total: a few minutes to set the gauge, read the city pressure, and shut off the meter, then a 15-minute wait to see if the pressure holds. In the video, we gave it 16 minutes and watched the system lose about 10 PSI — a confirmed leak.
A water leak test checks whether the home’s existing water pressure holds when the supply is shut off — no pressure is added. A hydrostatic test pumps the system up above normal pressure, and is typically used to test sewer and drain lines. On a suspected slab leak, plumbers run both: one for the water system, one for the sewer.
Yes — the basic test only requires a hose bib pressure gauge and the ability to shut off the water at the meter. Remember to isolate irrigation systems, avoid using any water during the 15-minute wait, and turn the water back on when finished. Finding the exact location of a confirmed leak, however, requires professional listening equipment and training.
A pressure drop means water is escaping somewhere between the meter and the home’s fixtures — a leak. The next step is isolating sections (yard line vs. under the house) and then pinpointing the leak with professional acoustic equipment before any digging or cutting begins.
Yes. The test checks the pressurized water system, so it works on any foundation type — slab, pier and beam, basement, or crawlspace. The house in our video was pier and beam, and the test confirmed a leak in about 16 minutes.
