How to Fix a Leaking Faucet: Cartridge, Compression, and Ball Valve
A step-by-step LA-tested guide to diagnosing and fixing the three most common faucet types in homes built between 1920 and today.
TL;DR
Most faucet drips are caused by a worn cartridge, washer, or O-ring — a $10 part and 30 minutes of work. Identify your faucet type first (cartridge, compression, or ball), shut off supply, swap the worn component, reassemble. The hardest part is usually loosening corroded mounting nuts on older LA homes.
What’s in this guide
- Identify your faucet type
- Gather tools and shut off water
- Disassemble the handle
- Replace the cartridge or washer
- Reassemble and test
- Common mistakes to avoid
- When to call a pro
About 60% of the leaking-faucet calls we run in Los Angeles are repairable with a single $10 part and 30 minutes of careful disassembly. The other 40% need full faucet replacement because the underlying valve body is corroded beyond repair. This guide walks through how to tell the difference, plus the specific quirks of each common faucet type — cartridge, compression, and ball — that we see in pre-war Hollywood bungalows, mid-century San Fernando Valley ranches, and post-2000 high-end fixtures alike.
Tools & Materials You’ll Need
Tools
- Adjustable wrench
- Flathead and Phillips screwdrivers
- Allen key set (metric and SAE)
- Channel-lock pliers
- Replacement cartridge or washer kit (specific to faucet brand)
- Plumber’s grease
- Old towel or rag
- Vinegar (for soaking corroded parts)
Materials
- Replacement cartridge ($15–$45)
- Or rubber washer + O-ring kit ($4–$12)
- Replacement ball valve assembly ($15–$25)
- Plumber’s tape (PTFE)
- Penetrating oil (PB Blaster or similar)
Step-by-Step Instructions
Identify Your Faucet Type
Look at the handle. Single handle that lifts AND rotates = cartridge or ball valve. Two separate handles (one hot, one cold) that rotate but don’t lift = compression. Cartridge faucets are most common post-1985 (Moen, Delta, Kohler). Ball valve was popular 1970s–1990s (Delta especially). Compression is found in pre-1960 homes and budget builders.
Shut Off the Water Supply
Find the angle stops under the sink — small valves on the supply lines. Turn each clockwise until tight. Open the faucet to verify no water flows and to relieve pressure. If your angle stops are seized (common on 1960s–70s LA homes), shut off at the main supply instead.
Remove the Handle
Most cartridge faucets have a small decorative cap on top of the handle. Pry it off carefully with a flathead. Underneath is a Phillips or Allen-head screw — remove it. The handle should pull straight up; if it’s seized, gently rock it side-to-side or apply penetrating oil and wait 10 minutes.
Access the Cartridge or Valve Body
For cartridge faucets, you’ll see a retaining nut or clip holding the cartridge in place. Remove it carefully. For compression faucets, unscrew the bonnet nut to expose the valve stem. For ball valves, remove the cap, cam, and packing using the brand-specific tool (usually included in repair kits).
Inspect and Replace the Worn Part
Pull out the cartridge, washer, or ball assembly. Look for visible wear, cracks, or mineral buildup. Match it exactly to the replacement (bring the old one to the hardware store if unsure). For compression faucets, replace BOTH the rubber washer and the brass seat (a $4 seat-replacement tool from any hardware store handles this in 5 minutes).
Lubricate and Reassemble
Apply a thin layer of plumber’s grease to the new cartridge or washer’s O-rings before installation. Reverse the disassembly steps. Hand-tighten retaining nuts first to avoid cross-threading, then snug with a wrench — don’t overtighten.
Turn On Water and Test
Slowly open the angle stops. Turn the faucet on and off through its full range — hot, cold, mixed. Check for drips at the spout AND under the sink at the supply connections. Leave a paper towel under the faucet body and check after 30 minutes for slow leaks.
Across LA single-family homes from the 1950s onward, two faucet failure patterns dominate. First, hard-water mineral buildup on cartridge O-rings — the cartridge isn’t actually broken, but the rubber has hardened against scale to the point that water finds new paths around it. Vinegar-soaking the cartridge for 45 minutes restores most of these without replacement. Second, the supply-line braided stainless lines are a 7–10 year wear item that almost no homeowner replaces preventively; we’ve seen catastrophic floods at year 11–13 when the rubber liner inside the braid finally splits. If your faucet is older than 10 years, replace the supply lines with the cartridge.
Don’t over-tighten retaining nuts
Cracked faucet bodies are the #1 reason DIY faucet repairs become full faucet replacements. Snug, don’t crank.
High water pressure can defeat any repair
If your home pressure is above 80 PSI (test with a $12 hose-bib gauge), even a perfect cartridge swap will fail again within months. Fix the pressure regulator first.
Real Scenarios from Our LA Service Calls
1928 Compression Faucet, Repeat-Drip Caller
A homeowner in Whitley Heights had replaced the same washer four times in two years. We pulled the bonnet nut and found the brass seat at the bottom of the valve body was pitted and unable to seal. Reseated with a $4 seat-removal tool, installed a fresh washer, and the drip stopped permanently. Total time on-site: 35 minutes.
2014 High-End Cartridge, Slow Leak Behind Wall
A homeowner reported a barely-visible water stain under their master sink. The drip wasn’t at the faucet at all — it was a hairline crack in the supply hose to the cartridge, dripping inside the cabinet wall cavity. Replaced both supply hoses with corrosion-resistant braided stainless ($28 each) and the cartridge as a precaution. Total: $260 for parts and labor.
When to Call a Plumber Instead
DIY isn’t always the right call. Bring in a licensed plumber if any of these apply:
- You’ve replaced parts twice and the leak persists
- The faucet body itself is cracked or visibly corroded
- The supply lines under the sink are leaking (these can be tricky to replace cleanly)
- Your shutoff valves are seized and won’t close
- The leak is inside the wall behind the faucet (likely a supply line failure, not the faucet)
- The faucet is over 15 years old — replacement is usually more cost-effective than repair
Frequently Asked Questions
How much does it cost to fix a leaking faucet?
DIY: $4–$45 in parts depending on faucet type (washer kit cheapest, name-brand cartridge most expensive). Plumber service call in LA: $185–$385 for a basic cartridge swap, more for older or premium fixtures requiring specialty parts.
Why does my faucet drip again after I replaced the cartridge?
Most common cause: the new cartridge is the wrong sub-model for your specific faucet (manufacturers make 5–8 variants per brand). Second cause: high water pressure (above 80 PSI) wearing the new part faster than normal. Third: damaged valve seat that wasn’t replaced.
Can I use any cartridge or do I need brand-specific?
Brand-specific. Moen, Delta, Kohler, Pfister, and Grohe each use different cartridge designs. Universal cartridges exist but rarely fit perfectly and tend to fail faster. Bring your old cartridge to the hardware store or call your faucet manufacturer with the model number.
How do I tell if my faucet is cartridge, ball, or compression?
Single handle that lifts to turn on/rotates to mix temperature = cartridge or ball. Cartridge feels smooth in operation; ball feels slightly notchy. Two separate hot/cold knobs that rotate (don’t lift) = compression. Pre-1985 single-handle is usually ball valve (Delta especially).
Should I just replace the whole faucet?
Replace if: faucet is over 15 years old, the body is corroded, the finish is peeling, or you’ve already done major repairs. Repair if: the faucet is under 10 years old, in good condition, and the leak is at a wear point (cartridge, washer, O-ring).
How long should a repair last?
5–8 years for a cartridge replacement, 2–4 years for compression washers (rubber wears faster), 8–12 years for full faucet replacement. Hard LA water shortens these intervals; if you have a softener, expect the longer end of each range.
Need professional help in Los Angeles?
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