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
References
- Manufacturer service manuals (Moen, Delta, Kohler, etc.)
- IPC + UPC plumbing codes
- Lead-free legislation
- Manuall internal: Plumbing Fixtures Reference, Common Pipe Fittings