Welcome to part five of our Leak Inspection and Repair Blog Series that explores bathroom leaking causes and solutions. This article focuses on how to repair one-handle shower valves.

Do you believe your bathtub could be leaking? If so, it’s important to handle any needed repairs as soon as possible. Avoid costly and even dangerous water damage in your home by first assessing where your bathtub leaking is coming from. If you believe the source could be a defective shower valve, read more to learn how to tell if your shower valve is leaking and how to repair a leaking shower valve for one-handle Moen fixtures. 

If you’re looking for repair tips for two- or three-handle shower valves, read part four of the series: Guide to Repair Shower Valve Leaking for Two- or Three-Handle Fixtures.

How To Tell if Shower Valve Is Leaking

A leaking bathroom can significantly drive up your water bill. It can also cause extensive water damage, resulting in mold and rot spreading throughout your home. The first step to preventing further damage is to pinpoint where your leak is coming from.   

If you notice constant dripping from your bathtub spout or shower head after the water is turned off or loss of hot water, your problem could be a leaking shower valve. These signs often mean the valve behind the shower handle (i.e., the fixture you use to turn your water on and off) is faulty and you need to know more than how to change a shower head.

Repair Tools for Leaking Shower Valve

If you’ve identified that your one-handle shower valve is leaking, it’s important to fix the problem as soon as possible to prevent further damage. Thankfully, repairing a leaking shower valve is a fairly easy plumbing project that you usually complete yourself. 

Here’s a list of materials you’ll need to fix a one-handle Moen shower valve: 

• Pocket knife/utility knife
• Phillips head screwdriver or allen key
• Needle-nose pliers
• Calcium, Lime and Rust Remover (CLR) (optional)
• Speciality cartridge removal tool (optional)
• Cartridge replacement kit
• Tub/shower valve socket wrench (optional)
• Specialty faucet handle remover (optional)

How To Fix A Leaking Moen Shower Valve

Step 1: Prepare to fix leaking shower valve

• Turn off your water supply valve to prevent any water damage while you’re making the repair.
  • You can either turn off the water that’s directly supplied to your bathtub/shower (if you have an accessible shut off valve). Otherwise, find your emergency water shut off valve and turn off the water to your entire house.
• After turning off the water, open the shower valve faucet to release any pressure within the pipes.
• Cover your tub drain with a towel to prevent objects from dropping down the drain and to protect the bottom of your bathtub.

Step 2: Expose working parts of the leaking shower valve

• Examine your shower handle for screws. If you don’t see any, they might be hidden underneath a plastic or metal covering at the center of your faucet handle.
  • If no screws are visible, pick at the seam of the covering with the utility or a pocket knife until it pops off.
  • Look behind the covering for the screws that attach the handle to the wall.
• Remove the handle by unscrewing it with either a Phillips head screwdriver, allen wrench, or hex key for set screws.
• Next, remove the decorative faceplate or escutcheon from the wall.
  • It’s usually attached by two or more screws. Locate them and unscrew the faceplate from the wall.
  • You may need to score (by running a utility knife around) the edge of the faceplate to break the caulked seal if it was caulked to prevent leaks.
  • The faceplate should now come right off to expose the shower valve cartridge.
    • Important note: If you discover leaking behind the wall when you remove the faceplate, call in a plumber. You’ve got a bigger problem than a faulty shower valve.
• If a chrome sleeve is covering the main shower body, simply pull it off to expose the shower valve body and cartridge.
  • The sleeve is held on by friction and should come off by gently pulling on it.
  • Once it’s removed (or if it’s not present) you should be able to see the main shower valve body that contains the cartridge you’ll be removing and replacing.

Step 3: Remove and replace the faulty shower valve cartridge

• First, remove the retainer clip that’s holding the cartridge in place.
  • The retainer clip is located toward the front of the shower valve body sticking out of the wall. Carefully remove it by grasping it with needle-nose pliers and pulling straight up.
    • Be careful not to drop it inside the wall.
• At this point, you now can access and replace the valve cartridge.
  • The cartridge is centered inside the shower valve body. Since it’s sat there for some time, you may need to first let it soak in Calcium, Lime and Rust Remover (CLR) before attempting to remove it.
    • If you tug gently and it’s stuck, you can use a special cartridge removal tool. (Sometimes the replacement cartridge you’ve purchased will include one as part of its kit.) 
  • Place the cartridge replacement tool over the brass stem of the shower valve body. The tool has a pair of shoulders that fit inside the shower valve stem and catch onto the corresponding shoulders of the cartridge inside of it. 
  • Using a pair of pliers, hold onto the square piece of the tool and twist a quarter of a turn to loosen the cartridge.
  • Twist back and forth until the O-ring seal breaks, signaling that the cartridge is now free to be removed.
    • Be careful as you twist. If the shower valve body cracks or breaks from too much pressure, you will have to replace the entire valve system. 
  • Grasp the end of the cartridge with needle-nose pliers and pull it firmly but gently straight out of shower valve body in the wall. 
• Install the replacement cartridge.
  • Begin by applying lube to the rubber seals and O-ring on the new cartridge. This helps ensure it doesn’t get stuck in the future and turns smoothly.
  • Insert the cartridge into the valve stem body, making sure it faces the right direction—with the HC indicator on top. Push it straight in without turning.
    • If you accidentally replace it upside down, you will reverse the direction of hot and cold for your shower. 
    • The cartridge needs to be pushed in all the way to avoid leaks.
  • Push the retainer clip back into its spot on top of the shower valve to hold the cartridge in place. Make sure you push it all the way in for a tight hold.

Tada! You have now replaced your shower valve cartridge. You can now skip ahead to step four to reinstall the shower valve covering and handles or you can keep reading here to learn how to install a restrictor valve on the cartridge to set a temperature limit.

How To Add a Restrictor Valve

• First, check your current water temperature. Since the handle of your faucet is not yet connected, grasp the shower valve with a pair of pliers and turn on the hot water to full blast.
  • You will have to turn your water supply back on to do this.
  • Use a thermometer to measure the water temperature. Less than 120 degrees Fahrenheit is considered ideal (and less than 115 degrees Fahrenheit if the bath will be used for young children.)
• If you decide you want to set a temperature upper limit, install the restrictor valve or limit stopper by turning it 90 degrees to the right and pushing it into place at the end of the shower valve cartridge.
• Use pliers to turn on the hot water again and the thermometer to check the temperature.
• If you want to restrict the temperature further, turn the restrictor valve further to the right. If you want the water to be able to get warmer, turn the valve further to the left.

Handle Reinstallation Using Mounting Pieces

• Friction fit the chrome sleeve that covers the shower valve stem back into place by turning it clockwise by hand.
• Place the decorative faceplate/escutcheon back in its spot.
  • Reinstall whatever screws held it in place (usually one on the top and bottom, or one on each side).
  • For a better leakproof seal, caulk around the outside edge of the faceplate.

• Replace the shower handle as you removed it, by screwing it in and putting back the plastic or metal covering that concealed the screw, if applicable. (See below for how to install a handle that requires mounting pieces.)
• Turn your water back on, then check and make sure the handle is working properly.

You have now fixed your leaking shower valve and can enjoy consistent temperatures in your shower without any dripping. If you’re in need of more thorough leak detection and repair solutions or are looking for a reliable plumber in Rockville, MD, or the surrounding areas, contact Heil Plumbing DMV today.

Look out for more articles from our Leak Inspection and Repair Blog Series, which overview:

• Part 1 – 4 Main Causes of Pesky Bathtub Leaking
• Part 2 – Bathtub drain leaking (waste drain repair)
• Part 3 – Bathtub overflow drain leak repair
• Part 4 – Shower valve leaking repair (for two- or three-handle valves)
• Part 5 – You’re here.
• Part 6 – Adjusting Your Trip-lever Drain Stopper – ​​Why Your ​​Tub Doesn’t Hold Water

If you ever find yourself in a fix and need leak detection in Rockville and the surrounding areas, connect with a trustworthy plumber in Baltimore County by contacting Heil Plumbing today.

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Heil Plumbing is a family-run company owned by a third-generation master plumber. We can help you with a full range of plumbing services, including toilet installation and repair, leak detection and pipe repair, faucet repair and installation, drain cleaning, and water heater repair in Baltimore County and the surrounding areas.