Common Faucet Diagnosis Reference
Why this matters
Faucets are common service calls - leaks, low flow, drips, handle issues. The tech who diagnoses faucet types + common failures works efficiently. This is the field card.
Faucet types
Compression faucet (older):
- Separate hot + cold handles
- Washer compresses against seat
- Drip when washer worn
Ball faucet:
- Single handle (often kitchen)
- Ball with hole controls hot / cold mix
- Wear leads to leaks
Cartridge faucet:
- Single OR double handle
- Cartridge controls flow
- Most common modern
Ceramic disc:
- Single handle typically
- Ceramic discs slide
- Long-lasting; resists wear
- Common premium
Common faucet problems
Dripping faucet (most common call):
- Compression: washer worn
- Ball: O-rings OR seats worn
- Cartridge: cartridge worn / O-rings
- Ceramic: ceramic seal damaged
Won't shut off:
- Same as dripping but extreme
- Cartridge / washer / seal failure
Low flow at faucet:
- Aerator clogged (most common)
- Cartridge clogged
- Supply restriction
- Hard water buildup
Hot OR cold only works:
- Cartridge issue
- Internal valve issue
- Cross-connection somewhere
Handle wobbly / loose:
- Stem nut loose
- Cartridge worn
- Hardware issue
Spray head not working (kitchen):
- Diverter failed
- Hose damaged
- Spray head clogged
Leak under sink:
- Supply line connection
- Drain assembly
- Faucet body crack (rare; replace faucet)
Diagnosing the faucet type
Visual indicators:
- Two handles + simple = compression
- Single handle + cap on top = ball
- Single OR double + cartridge brand label = cartridge
- Single handle + smooth modern look = ceramic disc
Brand label:
- Most faucets stamped
- Identifies type + parts available
Repair sequence
For dripping faucet:
- Shut off water supply (under sink)
- Open faucet to drain pressure
- Disassemble per faucet type
- Inspect components
- Replace worn parts (washer, O-rings, cartridge, etc.)
- Lubricate (silicone grease usually)
- Reassemble
- Open water supply slowly
- Test for leaks
Cartridge replacement
Most-common faucet repair today:
Process:
- Shut off water
- Remove handle (set screw OR cap + screw)
- Remove handle nut / collar
- Pull cartridge out (sometimes specialty puller)
- Verify replacement matches
- Install new
- Reassemble in reverse
Common brands:
- Moen
- Delta
- Kohler
- Price Pfister
- Each has specific cartridges
Compression faucet repair
Washer replacement (older approach):
- Remove handle
- Remove packing nut
- Pull out stem
- Remove washer screw at bottom of stem
- Replace washer (proper size + material)
- Replace packing if needed
- Reassemble
Sometimes also replace seat:
- Brass seat at bottom of valve
- Reground with seat reseating tool OR replaced
- Cause of recurring leaks
Ball faucet repair
Repair kit typically:
- O-rings (multiple)
- Springs + seats (under ball)
- Ball (if worn)
- Cam + packing
Process:
- Disassemble per manufacturer
- Replace components
- Lubricate
- Reassemble
Aerator cleaning
Common issue:
- Mineral deposits build up
- Reduces flow
- Affects spray pattern
Process:
- Unscrew aerator (some by hand; some need tool)
- Soak in vinegar 1-2 hours
- Brush clean
- Rinse
- Reinstall
If badly clogged: replace.
Spray head (kitchen)
Common issues:
- Diverter failed (spray weak)
- Hose damaged
- Spray head clogged (mineral)
- Locked-up button
Replacement:
- Newer kitchen faucets: spray head removable
- Sometimes replace whole hose + head assembly
- Per manufacturer
Single-handle faucet adjustments
Hot vs cold balance:
- Some faucets have temperature limit
- Adjust per manufacturer
- Anti-scald protection
- Reset after repair
Common parts inventory
For service:
- Cartridges (Moen, Delta, Kohler common sizes)
- Washers (various sizes)
- O-rings (size assortment)
- Aerators (universal + brand-specific)
- Stem packings
- Faucet repair kits (per brand)
Diagnosis questions
For customer's complaint:
"My faucet drips":
- How long?
- Hot, cold, or both?
- When did it start?
"Low water flow":
- One faucet OR multiple?
- Hot, cold, or both?
- Recent change?
"Handle won't turn":
- Stuck mid-position
- Hardware failure
Tools
- Adjustable wrench (sometimes 2)
- Allen keys (set screws)
- Channel locks
- Cartridge puller (faucet-specific tools sometimes)
- Plumber's grease
- Silicone-based lubricant
- Replacement parts
When to replace whole faucet
Replace when:
- Body cracked OR corroded
- Brand discontinued (parts unavailable)
- Customer wants upgrade
- Multiple major failures
- Old + outdated
Repair when:
- Specific component failure
- Quality faucet (worth investment)
- Customer wants to keep existing
Faucet quality considerations
Premium brands:
- Moen, Delta, Kohler, etc.
- Lifetime warranty (often)
- Parts available decades
- Quality construction
Budget brands:
- Less expensive
- Limited warranty
- Sometimes proprietary parts
- Shorter life
For customer choosing:
- Worth investment for quality
- Long-term cost
- Manufacturer warranty support
Lead-free requirement
Federal: Reduction of Lead in Drinking Water Act
- Faucets must be lead-free (less than 0.25% lead)
- Older faucets sometimes don't comply
- Newer faucets all compliant
- Marked "lead-free" OR similar
For replacements: lead-free standard.
Specific scenarios
Customer's bathroom faucet drips for months:
- Diagnose type
- Replace cartridge OR washer
- Quick fix usually
Customer's kitchen sprayer weak:
- Diverter (most common)
- Replacement of diverter OR whole spray head
Customer's outdoor faucet leaks at handle:
- Packing OR stem worn
- Replace
- Anti-siphon valve sometimes
Customer's tub spout drips:
- Diverter (if shower combo)
- Stem / cartridge
- Replace
Customer can't get hot water at one faucet:
- Cartridge issue
- Cross-connection
- Specific to that faucet (other faucets OK)
Specialty faucets
Touchless / touch faucets:
- Battery-operated
- Sensors can fail
- Electronics + plumbing
- Different diagnosis
Filtered water faucets:
- Connected to filter system
- Filter clog reduces flow
- Sometimes separate filter housing
Pot fillers:
- Wall-mounted
- Cold water only
- Single-purpose
Bar / prep sinks:
- Same as standard
- Often smaller scale
Tubular faucet components
Spout:
- Where water exits
- Can be pull-out (kitchen) OR fixed
Aerator:
- At spout tip
- Mixes air with water
- Reduces splash
- Cleaning periodically
Base / body:
- Mounts to sink
- Contains valves
- Connects to supply lines
Customer education
Maintenance:
- Clean aerator periodically
- Don't over-tighten handles
- Quality water = longer faucet life
- Water softener helps in hard-water areas
When to call:
- Drips that don't stop
- Low flow despite cleaning
- Cracks visible
- Wobbly fixtures
Documentation
Faucet work is small-ticket and high-volume, which is exactly why the notes get skipped and exactly why they matter on the return visit.
Identify the fixture before you leave:
- Manufacturer, and the model or series if it is stamped, cast into the body, or printed under the escutcheon.
- Faucet type (compression, ball, cartridge, ceramic disc) and cartridge or stem part number.
- Photograph the faucet from the front and the underside of the deck. On a return trip with a part in hand, that photo saves a second trip.
Record the condition you found:
- Which symptom, which side (hot, cold, or both), and whether it was constant or on operation only.
- Supply stop condition. Seized, weeping, or missing stops are the reason a small faucet job turns into a bigger one, and the customer needs to hear it before you cut water.
- Existing damage: corroded deck, cracked sink, rotted cabinet base, prior water staining. Photograph it before you touch anything.
- Water pressure and any hard-water scale you observed. Scale explains repeat aerator and cartridge failures and sets up the softener conversation honestly.
Record the work:
- Parts installed with numbers, whether they were manufacturer or aftermarket, and the warranty term. Many manufacturers cover cartridges for the life of the fixture, and the customer should know their claim exists.
- Whether the shutoff valves were replaced or left, and the flow test result at full open, hot and cold.
Record what you recommended and what was declined: replacing corroded stops, replacing a fixture that is past parts availability, addressing pressure or water quality. Write the decline down.
Who reads it later: the next tech, your parts desk when the cartridge does not match, and the manufacturer's warranty desk. On a rental or commercial property, the owner also reads it when the same unit calls again.
References
- Manufacturer service manuals (Moen, Delta, Kohler, etc.)
- IPC + UPC plumbing codes
- Lead-free legislation
- Manuall internal: Plumbing Fixtures Reference, Common Pipe Fittings