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Understanding Common Faucet Leak Types and What Causes Them

Faucet leaks are one of the most common household plumbing problems. According to the U.S. Environmental Protection Agency, a single dripping faucet that leaks one drip per second can waste more than 3,000 gallons of water per year. That's equivalent to the amount of water needed to take over 180 showers. Understanding what causes different types of leaks is the first step toward addressing the problem in your home.

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Faucets leak for several reasons, and identifying the type of leak helps determine the best repair approach. The most common cause of leaks is worn washers and seals. Inside your faucet, rubber washers create watertight seals. Over time, these washers deteriorate from repeated use and exposure to water minerals. When a washer wears out, water drips past it even when the faucet is turned off. This typically happens in compression faucets, which are the older two-handle models still found in many homes.

Another frequent cause is corrosion or mineral buildup. Hard water contains minerals like calcium and magnesium that accumulate inside faucet valves and aerators. This buildup prevents the valve from closing completely, causing persistent drips or slow leaks. Corrosion occurs when metal parts inside the faucet oxidize, roughening the surfaces that should create a tight seal.

Damaged valve seats represent another common problem. The valve seat is the surface where the faucet stem connects with the faucet body. If this surface becomes cracked or eroded, water will leak from the spout even when the handle is turned off. Cartridge and ball faucets can develop leaks when their internal moving parts wear down, as these faucet types rely on precise mechanical tolerances to function properly.

Water pressure problems can also cause faucet leaks. Excessive water pressure forces water past seals that would normally hold under normal conditions. If your home has consistently high water pressure, you're more likely to experience leaks across multiple faucets and fixtures. Understanding these causes helps you explain the problem to a repair professional or determine whether a repair is within your capabilities.

• Worn washers and seals — the most common cause, especially in older compression faucets
• Mineral buildup from hard water that prevents valves from closing fully
• Corroded or damaged valve seats that no longer seal properly
• Worn internal cartridges or ball mechanisms in modern faucets
• Excessive water pressure that forces water past seals

Practical Takeaway: Before attempting any repair, observe where the leak originates — from the spout, handle, or base — as this tells you which internal component likely needs attention.

Tools and Materials You'll Need for Faucet Repair

Repairing a leaky faucet doesn't require an extensive toolkit or expensive equipment. Most repairs use basic tools that many homeowners already have in their homes. The specific tools needed depend on your faucet type and the nature of the leak, but a standard repair kit covers the majority of common faucet problems.

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The most essential tool is an adjustable wrench, which fits different bolt and nut sizes. A set of screwdrivers — both flathead and Phillips head — helps remove faucet handles and trim rings. An Allen wrench set handles the set screws found on many modern faucet handles. A flashlight or headlamp lets you see inside the faucet cabinet and under the sink clearly. Pliers, including standard slip-joint pliers and tongue-and-groove pliers, grip and remove various faucet components.

Specialized faucet tools make repairs easier, though they're not always necessary. A valve seat wrench removes the valve seat from compression faucets — a hexagonal component that's difficult to access without the right tool. A faucet cartridge puller removes cartridges from modern faucets without damaging them. An aerator removal tool or strap wrench unscrew aerators without scratching the finish. These specialized tools cost between $8 and $30 each and are available at hardware stores or online.

Materials needed for repairs vary by repair type. Washers and seals come in replacement kits specific to your faucet model, typically costing $5 to $15. O-rings, small rubber rings that create seals, are often included in washer kits. Plumber's grease or silicone grease lubricates seals and helps them function properly. White vinegar cleans mineral deposits from aerators and valve components — you likely already have this at home. Teflon tape or pipe dope seals threaded connections and prevents leaks around the base of the faucet.

Before purchasing anything, identify your faucet type. Check under the sink or look at the faucet itself for the manufacturer name — common brands include Moen, Delta, Kohler, and Pfister. Write down any model numbers visible on the faucet or underneath. Bring a photo to the hardware store, as staff can help identify the correct replacement parts for your specific model. This prevents purchasing parts that won't fit your faucet.

• Adjustable wrench and standard wrench set
• Screwdrivers (flathead and Phillips head) and Allen wrench set
• Flashlight or headlamp for visibility
• Pliers including slip-joint and tongue-and-groove styles
• Washer and seal repair kits specific to your faucet model
• O-rings and rubber gaskets
• Plumber's grease or silicone grease
• White vinegar for mineral deposit removal
• Teflon tape or pipe dope for threaded connections

Practical Takeaway: Before buying any materials, determine your faucet type and model number — this single step ensures you purchase components that will actually work with your specific faucet.

Step-by-Step Repair Process for Compression Faucets

Compression faucets are the older two-handle or three-handle style faucets where turning the handle tightens or loosens a stem to control water flow. These faucets are common in homes built before 1980 and are generally the easiest to repair because parts are inexpensive and readily available. The repair process involves replacing worn washers and seals that prevent water from shutting off completely.

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Start by turning off the water supply to the faucet. Look under the sink for shut-off valves on both the hot and cold water lines. Turn these valves clockwise until they stop — don't force them. If shut-off valves aren't present or don't work, you'll need to shut off the main water supply to your house. Once water is off, turn on the faucet to release any remaining water pressure in the lines.

Next, remove the handle. Most compression faucets have a decorative cap or index button on top of the handle that pops off with a flathead screwdriver. Underneath is a set screw that holds the handle in place. Remove this screw and pull the handle straight up and off. If the handle is stuck, apply penetrating oil and wait 15 minutes before trying again.

With the handle removed, you'll see the packing nut — a hexagonal nut at the base of the stem. Use an adjustable wrench to turn this nut counterclockwise. Once loose enough, you can unscrew it by hand. Under the packing nut is packing material or a packing washer. Remove this, noting how it was positioned. Some newer compression faucets use an O-ring instead of traditional packing material.

Now remove the stem by turning it counterclockwise with your hand. It may come out easily or require gentle rocking back and forth. At the bottom of the stem, you'll find the washer held in place by a brass screw. This washer is typically what causes the leak. Remove the brass screw — use a screwdriver that fits snugly in the slot to avoid stripping it. Replace the old washer with a new one of the same size. While you have the stem out,