Common Causes of a Leaking Faucet (and How to Fix Each One)
Common Causes of a Leaking Faucet. A faucet that drips even after it's fully shut off is one of the most common plumbing complaints, and also one of the most fixable without professional help. A single dripping faucet can waste over 3,000 gallons of water a year, so it's worth tracking down the cause rather than living with the sound. The fix depends heavily on what type of faucet you have.
Know Your Faucet Type First
Modern faucets generally fall into four mechanical types: compression (two separate hot and cold handles, common in older homes), ball, cartridge, and ceramic disc. Knowing which type you have determines which internal part is likely worn out, since each design fails in a different way.
Cause 1: A Worn Washer (Compression Faucets)
If you have a compression faucet with separate hot and cold handles, the most common cause of dripping is a worn rubber washer inside the valve seat. Every time you turn the handle, that washer presses against the seat to stop flow, and repeated friction gradually wears it down until it no longer seals completely, especially from the hot water side where heat accelerates wear.
Fix: Shut off the water supply, remove the handle and packing nut, pull out the stem, and replace the washer at the bottom (usually held by a small brass screw) with an exact match from a hardware store.
Cause 2: A Damaged O-Ring
Cartridge and ball-type faucets use small rubber O-rings to seal various points inside the faucet body. Over time these can dry out, crack, or shift out of position, leading to a drip from the base of the spout rather than the tip. This shows up as water pooling around the faucet's base rather than dripping from the spigot.
Fix: After shutting off water and disassembling the faucet handle, locate the O-ring (often near the base of the stem or cartridge) and replace it with a same-size replacement.
Cause 3: A Worn Cartridge
Cartridge faucets (single-handle, common in many kitchens and bathrooms) rely on an internal cartridge to control both flow and temperature mixing. When it wears out, you may notice dripping along with the handle feeling loose or harder to move smoothly.
Fix: Cartridges are designed to be replaced as a single unit rather than repaired. Bring the old cartridge to a hardware store to match it exactly, since cartridge designs vary significantly between manufacturers and even between product lines from the same brand.
Cause 4: Corroded Valve Seat
The valve seat is the point where the faucet's internal stem connects to the spout. Mineral deposits from hard water can accumulate here over years, leading to corrosion that causes leaks around the spout area even with new washers installed.
Fix: A valve seat can sometimes be resurfaced using an inexpensive seat-grinding tool, or replaced outright on faucets designed with a removable seat. If corrosion is severe, this is a good moment to consider whether replacing the entire faucet makes more economic sense than repeated small repairs.
Cause 5: High Water Pressure
If several faucets throughout the house are dripping, unusually high water pressure could be stressing all of them simultaneously rather than each one failing independently. Residential pressure above 80 psi accelerates wear on every washer, O-ring, and seal in your plumbing system. A pressure gauge on an outdoor spigot will tell you if this is a contributing factor, and a pressure-reducing valve can be installed to bring it back into the normal range.
A Quick General Repair Checklist
- Always shut off the water supply to that fixture before disassembling anything.
- Take a photo of each step as you disassemble, so reassembly is straightforward.
- Bring old parts to the hardware store rather than guessing at sizes.
- Apply plumber's grease to new O-rings and washers before installing them to extend their life.
When to Call a Plumber
If you've replaced the obvious wear parts and the faucet still drips, or if you're not comfortable disassembling the fixture yourself, a plumber can typically diagnose and repair a leaking faucet in well under an hour.