Fix or Replace Bath Tub Mixer Cartridge - Moen

I have recently had a problem with my Moen mixer for the bathtub.  As I searched the Internet for some insight before I attacked the faucet, I found very little in the way of images or step by step instruction.  So, being a long time Maker and long time Instructables user / contributor, I thought I would fix that issue and share what I learned.  In fact, I will take things an extra step and say that if you are careful, you may be able to actually fix the problem without a new cartridge.

My mixer control is shown below.  You simply rotate the handle to get the right temperature.  On models that require you "pull out" first and then turn to "mix" this information probably will not be as helpful.

I needed the following tools:

Allen Wrench (only for handle set screw)
Vise Grips
#2 Phillips Screwdriver
Standard Screwdriver (small)

Step 1: Safety First and Then an Ounce of Prevention

Let me just say, be careful, wear safety goggles and keep your face clear of injury.

Next, turn off your water at the main inlet to your house and release the pressure by running a faucet nearest the mixer until there is no more running water.

Now an ounce of prevention, close the drain, plug the drain or cover the drain.  Losing a screw down the drain would really make this a whole new kind of job with added trips to the plumbing supply or hardware store.

Step 2: Remove the Mixer Handle

Locate the set screw that holds the mixer handle and remove it.

Step 3: Remove the Nylon Guides

Locate another set screw at the tip of the brass mixer spindle.  Remove it and the nylon pieces that it retains.  Follow through by removing the chrome or brass cover tube that keeps the internals from showing.

Step 4: Remove Cartridge Retaining Clip

I used a small Allen wrench through the retainer clip to gently pry up and get the retainer loose.  Check the photos for a clear view of what I'm trying to describe.

The retaining clip must be removed completely and set aside.

Step 5: Pulling the Cartridge - the Hard Part

This is the hard part.

There is a lot of rubber surface area which may have grown attached to its surroundings inside the pipes.  Getting the cartridge to start moving was a task.  Most important, you do not want to break something inside the wall by prying or tugging too hard.

What I did:

I took the Nylon fittings and reversed the white ones so that they were longer by the length of the geared section, (back to back instead of front to back), then I placed them over the exposed spindle.

Next I placed the black Nylon piece into its original home, inserted the screw and slowly tightened.  This created mechanical force between the pipe and the cartridge that literally leveraged the cartridge forward almost 0.25 of an inch.

Once the cartridge began to move, I removed the Nylon parts and set them aside again.

Now, using vice grips on the flats of the spindle I was able to pull straight out to remove the cartridge.  This still took quite a bit of effort.

In the second image, you can see the cartridge almost free of the pipe.

Step 6: Fix or Replace

If you are replacing the cartridge, simply wipe the inside of the pipe to clean it and then use a little plumbers grease on the rubber parts of the new cartridge and reverse the steps from here.

If you want to try a fix:

The next few steps are for taking apart the cartridge and there is no guarantee this is your problem or that it will fix anything.  In fact, it may just finish off the cartridge completely, but at least you will know how the darn thing works. : )

Step 7: The Cartridge Exposed

In this image, you can see the most obvious components.  Inside the mixer is a two layer moving section, one that moves specifically with the spindle and one that moves by water flow.

Step 8: Dissasembly of the Cartridge

First, push the spindle into the cartridge so that the insides are forced out the back.  Note that the rubber gaskets that separate the Hot and Cold water are all that keep this together. 

Once it starts to move it should become easier to slide out.

Remove the inside section completely as shown in the second photo.

Step 9: Remove the Plastic Retainer

Using a very small screwdriver or blade type tool, very carefully pry all around the edge of the plastic retainer.  It will only come up a teeny bit before it lets go.

Set the retainer to the side.

You can now try simply dumping the last part out of this section of the cartridge since the retainer is no longer there to keep it.  However, if it does not freely fall out, this may be the problem with the cartridge.

Using a flat blade screwdriver, insert the screwdriver into the end where the retainer was and gently twist the inside section to break it loose.  Next, using the holes along this unit, help the inside piece to come completely out.

Step 10: Clean Everything and Reverse the Process

OK.

If you came this far, hopefully you discovered that inner piece was stuck and causing problems.  Now, you need to clean everything.  You may want to soak the parts a few minutes in vinegar and then rinse with water before re-assembly.  Keep in mind your water is still turned off and turning it on would be messy right now.  I wiped my parts really well with a rag and was successful.

Simply reverse this whole process for re-assembly, pushing parts together and being careful not to bend, flex or otherwise do anything to break them.  Applying some plumbers grease can make the re-assembly easier.

I hope this helps you as much as it helped me. : )


By the way, don't forget to double check everything and that the retaining clip is installed before you turn your water back on.

Now that you have a fully functional bath tub, get some candles and bubble bath for your valentine!