Leak Detection Methods Reference

Why this matters

Hidden leaks cause B+ in annual property damage. The tech who locates leaks efficiently saves customer + delivers value. Detection method depends on leak type. This is the field card.

Leak types

Water leak: plumbing supply OR drain; hidden in wall, slab, ceiling, OR underground.

Refrigerant leak (HVAC): small loss erodes system performance; major loss causes failure.

Gas leak: critical safety; explosive + asphyxiating.

Roof leak: water entry from above; difficult to trace.

Foundation / basement leak: water enters foundation; identifies water entry point.

Ducting leak: HVAC ductwork loses conditioned air (covered in duct sealing).

Water leak detection methods

Visual: wet spots, staining, peeling paint, sagging ceiling, bulging drywall, mold growth. Water meter test: shut all fixtures + read meter (movement = leak); isolate by section. Pressure test: pressurize with air OR water; observe pressure drop. Acoustic: sound amp equipment (Pole-Cat, SeekTech); mic on suspect pipe; best for pressurized supply. Thermal imaging: IR camera shows temp differences (warm pipe behind cold drywall = hot leak; cold spot = cold leak). Dye test: food coloring in toilet tank (flapper leak); pool dye (liner leak). Moisture meter: pin OR pinless; reads moisture in walls/floors; confirms wet area pre/post repair. Smoke test: for drain/vent; non-toxic smoke escapes from leak. Tracer gas (helium/nitrogen): pressurize with detectable gas; probe surface for escape; precise.

Refrigerant leak detection

Electronic detector (Fieldpiece SRL2, Inficon, Bacharach): halide/oxidation; sniff fittings; visual + audio trigger. UV dye: add UV-fluorescent dye to refrigerant; UV light reveals dye at leak; permanent system addition. Soap solution: brush on fitting; bubbles indicate leak; simple + visible. Standing vacuum test: pull deep vacuum (500 microns); hold; rise = leak. Pressure decay test: pressurize with nitrogen (250 PSI); drop = leak.

Gas leak detection

Smell of mercaptan (added odorant): obvious; evacuate + call utility. Electronic combustible gas detector (TIF8800, RIDGID Micro CD-100): audio + LED; sweep pipe seams + fittings. Soap solution bubbles on gas pipe joints + verify with electronic detector. Pressure decay test per NFPA 54: pressurize with air/nitrogen 25 PSI for 15 min; 0 PSI drop allowed. Don't use lighter/matches (explosion risk).

Roof leak detection

Visual inspection: stains, mold, sagging on interior; missing shingles, flashing failures, damaged seals on exterior.

Water test:

• Hose top of roof; observe interior
• Section by section; isolate leak

Smoke test (rare):

• Generate smoke inside attic
• Smoke escapes through gaps to roof exterior

Thermal imaging:

• Detect wet insulation in attic
• Heat retention differs from dry

Manual inspection:

• Walk roof; identify damage
• Inspect flashing, valleys, penetrations
• Common leak locations: flashing, valleys, around penetrations (chimney, vent, skylight)

Foundation / basement leak

Water source diagnosis:

• Surface water (rain runoff): grading issue
• Groundwater: high water table
• Plumbing supply leak: pinpoint with pressure test
• Plumbing drain: smoke test + dye
• Condensation: humidity issue (not leak)

Tracer dye + drainage: dye in suspect drain; observe in leak.

Outside vs inside: identify if water enters from outside (grade) OR inside (plumbing).

Slab leak

Symptoms:

• Warm spot on floor (hot water leak)
• Cracks in slab
• Wet carpet OR floor
• Unexplained high water bill

Detection:

• Acoustic leak detection through slab
• Thermal imaging
• Tracer gas + probe
• Pressure test individual lines

Repair:

• Re-route around slab (PEX OR copper through walls)
• Tunnel under slab
• Slab break + repair (last resort; expensive)

Underground leak

Symptoms:

• Wet patch on lawn
• Soggy area
• Mossy/green growth
• High water bill

Detection:

• Acoustic on water main
• Tracer gas
• Excavation if location uncertain

Service: locate + repair OR replace section.

Common leak detection mistakes

Skipping water meter test (most economical detection). Diagnosing wrong leak type (refrigerant detection methods don't work for water). Skipping electronic detector + relying on soap (some leaks too small for visible bubbles). Skipping vacuum test before refrigerant charge (charged with leak still present). Wrong test pressure for system (gas pressure on water system OR vice versa).

Sequence for water leak diagnosis

1. Visual inspection: obvious wet spots + signs.

2. Water meter test: confirm leak is in customer's system.

3. Isolate by section: shut off sections; identify branch with leak.

4. Pressure / acoustic / thermal: locate specific point within branch.

5. Confirm with secondary method: don't over-rely on single detection.

6. Repair + verify: post-repair, re-test for additional issues.

Refrigerant leak repair workflow

1. Locate leak (UV dye, electronic, soap).

2. Recover refrigerant (mandatory EPA).

3. Repair leak (braze, replace fitting, install line set).

4. Pressure test with nitrogen (250 PSI 15 min; 0 drop).

5. Evacuate to 500 microns.

6. Charge per nameplate (weighed).

7. Verify operation + retest leak detector (no leak).

Gas leak repair workflow

1. Evacuate area + shut off gas at meter.

2. Locate leak with detector + soap.

3. Repair joint (re-tighten OR re-thread + dope OR replace fitting).

4. Pressure test per NFPA 54 (25 PSI 15 min).

5. Verify all joints + downstream connections.

6. Re-open gas at meter; relight pilots / appliances.

Equipment costs (for service business)

When to refer

Slab leak in concrete pour: specialized; coring + concrete work.

Sewer line leak: camera + locator specialist.

Foundation crack: structural engineer.

Severe roof leak: roofing specialist.

Multiple system leaks: insurance claim + restoration company.

Customer education

Periodic leak check: water meter test annually.

Roof inspection: bi-annually + after major storms.

Refrigerant + gas systems: annual service includes leak check.

Don't ignore small water leaks: become big problems.

High water bill = potential hidden leak: investigate.

References

• EPA + EnergyStar water leak detection guidance
• ASTM standards for leak detection
• Manufacturer technical data (Fieldpiece, Inficon, RIDGID, FLIR)
• NFPA 54 (gas pressure testing)
• Manuall internal: Common Gauges + Meters, Diagnostic Test Procedures