Pressure
Testing
Pressure testing is how we determine if your pool's underground plumbing lines are intact or broken. We isolate each line — skimmers, main drain, returns, spa lines, water features — pressurize it, and monitor for pressure loss. A line that holds pressure is good. A line that loses pressure has a leak.
The Definitive Test for Underground Plumbing Leaks
Your pool has multiple underground plumbing lines running between the pool shell and the equipment pad: skimmer suction lines, main drain lines, return lines, spa lines, and water feature lines. When one of these lines cracks or separates underground, you lose water — but you can't see where because the leak is buried.
Pressure testing is the only way to definitively determine if a line is leaking. We isolate each line by plugging the openings, pressurize it to a controlled PSI, and monitor for pressure drop. A line that holds steady pressure is intact. A line that loses pressure has a leak somewhere along its length.
This isn't guesswork — it's diagnostic certainty. Before we dig, before we repair, we know exactly which line is leaking. That means we're not opening up your deck in the wrong location or replacing pipes that don't need replacing.
Schedule Leak Detection
Every Line Gets Tested Individually
A pool typically has 4 to 8 separate underground plumbing runs. We test each one individually so we know exactly which line is leaking — not just that "there's a plumbing leak somewhere."
Skimmer Lines
The pipe running from each skimmer back to the pump. Skimmer line leaks are common — especially at the skimmer throat connection buried just below the deck. If your pump loses prime or you see air bubbles in the pump basket, a skimmer line leak is a likely culprit.
Main Drain Line
The pipe running from the bottom drain to the pump. Main drain leaks are harder to locate because the pipe runs under the pool floor. If you can't run the pump on main drain alone without losing prime, the line may be broken.
Return Lines
The pipes running from the filter back to the return jets in the pool wall. Return line leaks lose water when the pump is running (because the line is under pressure). If you see wet spots in the yard near the return run, this is often the cause.
Spa suction and return lines if you have a spillover spa. Water feature lines for waterfalls, sheer descents, and deck jets. In-floor cleaning system lines if your pool has pop-up heads. Autofill lines if plumbed underground. Each line is isolated and tested individually.
How Pressure Testing Works
Pressure testing is a methodical process — each line is tested individually under controlled conditions.
Equipment Pad Inspection
We start at the equipment pad — checking valves, unions, pump connections, and visible plumbing for obvious leaks. This rules out above-ground issues before we test underground lines.
Line Isolation
We plug skimmers, returns, main drain, and other openings with test plugs to isolate each line. Valves are closed to separate suction side from pressure side. Each line becomes its own closed system for testing.
Pressurization
We connect a pressure testing rig to each line and pressurize it to 15-20 PSI using water or air. The line is filled and brought up to pressure gradually while we monitor the gauge.
Pressure Hold Test
We monitor the pressure gauge for 15 to 20 minutes per line. A line that holds pressure is intact — no leak. A line that shows pressure drop has a leak somewhere along its length. The rate of drop tells us about the severity.
Pass/Fail Report
You receive a clear report: which lines passed, which failed, and the pressure readings for each. If a line failed, we discuss next steps — either acoustic leak location to pinpoint the break, or repair/replacement options.
Pressure holds steady: Line is intact — no leak in this pipe.
Slow pressure drop: Small leak or crack — water is escaping gradually.
Rapid pressure drop to zero: Major break — the pipe is completely severed or separated underground.
Written Warranties on Plumbing Repairs
If we identify a leaking line and you proceed with repair, the repaired section is covered by our written warranty. Warranties are transferable to new homeowners at no additional cost.
Pool Pressure Testing — FAQ
Pressure testing is a diagnostic method used to determine if underground plumbing lines are intact or leaking. We isolate each line by plugging the openings, pressurize it to a controlled PSI (typically 15-20 PSI), and monitor the pressure gauge over time. If pressure holds steady, the line is good. If pressure drops, the line has a leak.
Most pressure tests are completed within 1 to 3 hours depending on the number of lines and the complexity of the plumbing system. Each line is monitored for 15 to 20 minutes to ensure an accurate reading. Pools with spas, water features, or in-floor cleaning systems have more lines and take longer.
No. Pressure testing is done with water in the pool. We plug the lines at the pool side (skimmers, returns, main drain) and test from the equipment pad side. The pool can remain full throughout the testing process.
We typically test at 15 to 20 PSI. This is higher than normal operating pressure (which is usually 10-15 PSI on the pressure side) but well within the safe range for PVC plumbing. Higher pressures are not necessary and can risk damaging older pipes or fittings.
The most common causes are ground movement (especially in DFW's expansive clay soils), tree root intrusion, improper original installation (missed glue joints), age-related deterioration, and freeze damage. Older pools with flex pipe or galvanized fittings are more prone to failure than newer PVC systems.
Common signs include unexplained water loss (more than normal evaporation), air bubbles in the pump basket or return jets, the pump losing prime, wet or soggy spots in the yard near plumbing runs, and higher-than-usual water bills. If your pool loses water faster when the pump is running, the leak is likely on the pressure (return) side.
If a line loses pressure, we know it has a leak — but we don't yet know exactly where along the line the break is. The next step is typically acoustic leak location: we pressurize the line with air and use listening equipment to hear where the air is escaping underground. This pinpoints the leak location so we know exactly where to dig.
It's possible but not recommended. Pressure testing involves working with pressurized systems, which can be dangerous if plugs blow out or fittings fail. Professional equipment and experience are needed to get accurate results and avoid damaging the plumbing. If you suspect a plumbing leak, it's worth having it done right the first time.
Suction side lines (skimmer, main drain) pull water from the pool to the pump. When they leak, they suck air into the system — causing air bubbles and prime loss. Pressure side lines (returns, water features) push water from the filter back to the pool. When they leak, they lose water when the pump is running because the line is under pressure. Pressure testing identifies which side — and which specific line — is leaking.
Main drain line repairs are more difficult because the pipe runs under the pool floor. Options include digging up and repairing the line (extensive work), abandoning the main drain and plugging it off (the pool can function on skimmers alone with proper circulation), or rerouting a new line around the pool shell. We discuss the options and help you decide based on cost and how critical the main drain is to your pool's operation.
Very accurate for determining if a line is leaking. A properly conducted pressure test gives a definitive pass or fail for each line — there's no guessing. The only limitation is that pressure testing tells you which line is leaking, not exactly where along the line the leak is. For that, we use acoustic leak location after the failed line is identified.
Yes. Pressure testing is a standard part of our comprehensive leak detection service. We test the pool vessel (shell, fittings, lights, skimmers) and the plumbing system (all underground lines). You receive a complete picture of where water is being lost.
Suspect a Plumbing Leak?
Air bubbles, prime loss, or unexplained water loss? Pressure testing identifies exactly which line is leaking — before we dig.
Last reviewed: April 2026