Common Leak Investigation Reference
Why this matters
Leaks come from many sources - plumbing, roof, HVAC, appliances. Water traveling from origin shows up far from the source. The tech who investigates systematically finds the cause efficiently + saves customer significant damage. This is the field card.
Why leaks are tricky
Water travels:
- Down through floors
- Along framing horizontally
- Through walls
- Around obstacles
- Stops at low point
Visible stain may be far from source:
- Ceiling stain in basement = roof leak (water traveled through walls + floors)
- Wet wall behind shower = leak in shower above
- Damp floor at corner = leak from above OR side
Don't assume source location.
Leak source categories
Plumbing supply (always under pressure):
- Pipe damage
- Fitting failure
- Fixture leak (faucet, toilet)
- Water heater
- Appliance supply lines
- Hose bibs
Plumbing drain (intermittent):
- Pipe damage
- Joint failure
- Trap leak
- Wax ring failure (toilet)
- Sink drain assembly
Plumbing vent:
- Roof penetration leak
- Connection failure
- Affects ceiling near vent
Roof:
- Shingle damage
- Flashing failure
- Penetration (vent boot, skylight)
- Ice dam (winter)
- Wind-driven rain
HVAC:
- Condensate drain clog (water from drain pan)
- Refrigerant line (theoretically refrigerant leak; rare water)
- Humidifier failure
- Duct condensation
Appliance:
- Dishwasher
- Washing machine
- Refrigerator water line
- Ice maker
- Water filter
Foundation / basement:
- Wall infiltration
- Floor crack
- Sump pump issue
Window / door:
- Flashing failure
- Caulk failure
- Sill damage
Diagnostic approach
When customer reports leak:
- Where is visible damage?
- When did it start? (Specific time = clue)
- Pattern? (Constant vs intermittent vs after rain)
- Worse when? (After shower, rain, AC running, etc.)
- What's above? (Often source above visible damage)
- What's nearby? (Plumbing, HVAC, appliance)
"When" reveals source
Constant leak:
- Supply line (pressure)
- Failed valve
Intermittent:
- Drain (only when used)
- Appliance (only when running)
- Toilet (intermittent unless flapper bad = constant)
After rain:
- Roof
- Flashing
- Window / door
After laundry / dishwasher:
- That appliance
- Drainage system
After shower:
- Shower drain
- Tile / grout failure
- Wax ring (if floor)
After HVAC runs:
- Condensate drain
- Refrigerant line condensation
- Drain pan overflow
Seasonal (worse in cold OR hot):
- Frozen pipe (cold)
- Condensation pattern (varies)
Visual investigation
Trace from visible damage:
- Look upward
- Follow stains
- Check structural members
- Walls + ceilings adjacent
Open access if needed (with customer permission):
- Drywall hole (small; patchable)
- Ceiling tile (drop ceiling)
- Access panel (sometimes existing)
Plumbing leak investigation
Supply line leak:
- Water meter test (verifies leak exists)
- Isolate sections with shutoffs
- Find leak point
Toilet leak (constant water):
- Flapper not seating
- Dye test (food color in tank; appears in bowl = leak)
- Fill valve cycling
Drain leak:
- Run water; observe under fixture
- Check trap connections
- Sometimes vinyl mat under to see drips
Slab leak:
- Under foundation
- Warm floor spot (hot water)
- Acoustic detection
- Specialty leak detection service
Roof leak investigation
Garden hose test:
- Customer + tech together
- Spray sections of roof methodically
- Other person inside watching for leak
- Often identifies source
Ice dam (winter):
- Snow melt + refreeze at eaves
- Water backs up under shingles
- Address attic insulation + ventilation
Wind-driven rain:
- Sometimes only specific wind direction
- Hard to replicate
- Multiple inspections may be needed
Vent boot failure:
- Common
- Visible at roof penetration
- Replace
HVAC leak investigation
Condensate drain clogged:
- Water in drain pan
- Float switch may have tripped
- Clear with shop vac OR pipe brush
Drain pan rusted / cracked:
- Replace pan
- Pan tablet treatments (preventive)
Refrigerant line condensation:
- Insulation degraded
- Water drips from suction line
- Re-insulate
Humidifier failure:
- Common modern systems
- Water line OR drain issue
- Inspect + repair
Appliance leak investigation
Dishwasher:
- Door seal worn (visible water below door)
- Inlet valve leak (constant)
- Pump leak (during operation)
- Drain hose connection
Washing machine:
- Inlet hose failure (catastrophic)
- Tub seal worn
- Pump leak
- Drain hose
Refrigerator water line:
- Behind unit
- Often saddle valve (notorious for leaks)
- Replace with proper shutoff
Ice maker:
- Water line behind freezer
- Sometimes internal valve
Slab leak diagnosis
For homes on slab foundation:
- Warm floor (hot water line)
- Higher water bill
- Sound of running water
- Specialty leak detection (acoustic, infrared)
- Decision: spot repair OR re-route
Tools for leak detection
Moisture meter:
- Quantify moisture in materials
- Pinpoint wet vs dry
Thermal imaging:
- See temperature differences
- Wet areas often cooler (evaporation)
- Hidden leaks visible
Acoustic leak detector:
- Listen for water rushing
- Slab leaks
- Underground
Tracer dye:
- Toilet dye test
- Drain dye for sewer infiltration
- Pool dye for liner leaks
Camera (sewer / drain):
- Internal view of drain
- Identify breaks, roots
Smoke pen / fog test:
- Plumbing vent inspection
- HVAC duct leaks
Common false leads
"Sweating pipes":
- Cold water in humid space
- Not actually a leak
- Insulate pipes; humidify control
Condensation on windows:
- Indoor humidity high
- Not building leak
Mineral staining:
- Looks like leak
- Actually old water mark (dried)
Multiple leaks:
- Sometimes
- Find one; check for others
Documentation
For leak investigation:
- Photos at each stage
- Customer's description
- Conditions (weather, time of day)
- Suspect sources investigated
- Source identified
- Repair done
For insurance / claims: thorough documentation essential.
When source unknown after investigation
Sometimes you can't immediately find:
- Recommend monitoring
- Customer logs occurrences
- Return for second investigation
- Specialty leak detection service
Don't pretend you know when you don't.
Customer education
After leak found + repaired:
- Where it was
- What caused it
- How to prevent recurrence
- Watch-for indicators
Stop the leak first
Immediate action when leak active:
- Shut off main water (plumbing)
- Catch water (buckets)
- Tarp roof (temporary)
- Move belongings
- Address damage assessment
THEN diagnose source.
Common leak mistakes
References
- IICRC S500 (Water Damage Restoration Standard)
- IICRC S320 (Building Drying)
- Manufacturer service manuals (appliances)
- Manuall internal: Common Leak Signatures, Moisture Intrusion Detection