How to Fix a Leaking Moen Kitchen Faucet

Moen is the king of cartridge faucets, owing to the fact that Al Moen, the company's founder, invented it. That simplifies Moen kitchen faucet repair because you don't have to spend a lot of time researching different faucet styles. If it's a Moen, it's a cartridge faucet.

That isn't to say that Moen doesn't offer a bewildering selection of faucet models. It definitely does. When a Moen kitchen faucet leaks, the fix often involves replacing the Moen kitchen faucet cartridge and/or the rubber parts that go with it, so you have to know what model of faucet you have so you can get the correct replacement parts. You can usually find this information online, either on a plumbing supply site or on Moen's own website.

If your Moen kitchen faucet is leaking from the spout, the cartridge isn't sealing water. The problem could be a damaged cartridge or worn seals. To access the cartridge, some disassembly is required.

1. Turn off the water valves under the sink and open the faucet to relieve water pressure.
   
   
2. Locate the screw cap on the faucet handle and pry it off with a flat-head screwdriver to reveal the set screw holding on the handle. The cap usually bears the Moen logo.
   
   
3. Loosen the set screw with a 1/8-inch Allen wrench and pull off the handle. It should come right off, but if it doesn't, a few light taps with a hammer should loosen the scale that is binding it.
   
   
4. Unscrew the retaining nut holding the cartridge using tongue and groove pliers. The cartridge may also be secured by a retaining pin. Work this out with a flat-head screwdriver, being careful not to lose it down the drain.
   
   
5. Pull out the cartridge by grasping the valve stem with pliers and wiggling it back and forth until it comes out. If the faucet is old, the cartridge may be stuck. If so, you may need to rent or buy a cartridge puller to remove it.

Once you have the cartridge in hand, examine it for cracks or nicks and replace it with a genuine Moen cartridge if you find any. If the cartridge is merely coated with scale, which is one reason it might leak, soak it overnight in a bowl of vinegar to dissolve the scale.

Replace all the O-rings on the cartridge if you decide to reuse it. You should also replace any gaskets inside the valve seats. You can remove these by sticking a screwdriver into the valve housing and prying them out. O-rings and gaskets are model specific and are usually available in kits.

If the faucet still leaks after you've serviced the cartridge, the valve seats are probably worn or nicked. Disassemble the faucet again and remove the valve seats with a seat wrench, which is available at any hardware store. You could have these reground, but it's easier and less expensive to simply replace them.

If a Moen single-handle kitchen faucet is leaking from the handle, or you see water dripping onto the sink deck, the O-rings around the base of the spout are worn. To service these, remove the handle and shimmy the spout up and off the top of the valve.

Replace all the O-rings on the outside of the valve body, lubricating each one with a small amount of plumber's grease before installing it. Clean the outside of the valve body and the inside of the spout before replacing the spout.