Why Does a Faucet Suddenly Become Stiff?

Over time, the handles on your sink, bathtub or shower faucet may become stiff, making them difficult or even next to impossible to turn. If you cannot turn the handles, using the faucet becomes unnecessarily difficult. Fortunately, replacing certain internal faucet parts restores the faucet to its normal operating condition.

...
Stiffness in a faucet invovles the rubber seals wearing out.

Ceramic Cartridges Vs. O-rings

Faucets that use ceramic cartridges do not become stiff versus a compression faucet that eventually does. Compression faucets use O-rings to create a watertight seal inside the faucet. As you twist the faucet's handles, the turning of the valve stem increases or decreases the flow of water through the faucet. Faucets with ceramic cartridges use rubber seats that sit at the openings between the faucet's ceramic cartridge and the body of the faucet, keeping the water from leaking through the connection and out the spout.

Seals Wear

The rubber O-rings inside your faucet wear out from age, exposure to air and exposure to heat from the hot water flowing through the faucet. As the faucet's seals wear out, the faucet does not turn as easily since the hardened O-rings create an increased amount of friction inside the faucet. If left inside the faucet, the aging O-rings will make turning the faucet's handles increasingly difficult and can also lead to leaks inside the faucet.

Replacing Seals

Once the seals in your faucet have worn out to the point you can no longer turn the handles easily, you must replace the seals with new seals. You must turn off the water to the faucet before you can take apart the handles to access the seals, which you can do using either the water valve handles found under the sink or in an access panel on the wall behind the shower or tub faucet. You may also use the house's main shutoff valve. Once you remove the faucet handles' retaining screws and pull off the handles, you must remove the valve stem or cartridge. Installing a new stem or cartridge requires you to take the old one to the store so you can find a perfect match, and then you can reassemble the faucet's parts.

Plumber’s Grease

Using plumber's grease on the new O-rings when you replace the old O-rings will help the rubber last longer and lengthen the amount of time that passes before you must service the faucet again. Home improvement and plumbing supply stores sell plumber's grease in either large containers if you plan to work on several faucets in the near future, or in small packets if you need plumber's grease for just one faucet.