Introduction: Fix or Replace Bath Tub Mixer Cartridge - Moen

Picture of 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

Picture of Remove the Mixer Handle

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

Step 3: Remove the Nylon Guides

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of Clean Everything and Reverse the Process


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!


philesra (author)2016-01-18

Very helpful in disassembling the cartridge, thanks!

mtairymd (author)2014-11-30

I just cleaned out my cartridge.. Thanks for the instructable!

Groundshine (author)2013-01-20

Didn't think this would work with a flat washer against the face but that 1/8 inch was all it took to get the cartridge moving! Made all the difference during installation to have the cartridge out - no worry about over heating. Thanks for posting this little tip.

tosenbach (author)2011-03-02

I just cleaned out my own Moen Cartridge and even though my cartridge is a little different, these instructions were spot on! My showers were always changing from scalding hot to freezing cold sporadically, but this fixed it. Make sure the water is turned off before you pull the unit out (I forgot!).

Getting it out is a bugger, but using a pliers or vise grip will help. I screwed the main screw back into the faucet and used it to pry the cartridge out (be careful not to ruin the threads). After you get the cartridge out, take off the black rubber pieces and try to pull the inner metal rod free from the plastic holder. It didn't immediately come out - I had to soak it for a while, as it had a lot of mineral buildup.

The only comment I'd suggest is to soak the pieces in vinegar for about an hour. Acetic acid (the power and smell of vinegar) does an amazing job of cleaning. All the metal pieces looked new again and the vinegar was a yucky grey/green color. It helps to have some water handy to rinse your hands before you do this as the tap will be turned off when you do it (or else you can use the toilet if you're brave enough). My cartridge looks brand new and its was originally installed in the 70's. Excellent tutorial!

elbruceo (author)2011-01-09

pulling one of these carts that's been install for several years can be tough I have replaced a few at my home A tool used in auto body repair The Slide Hammer works great

caitlinsdad (author)2010-01-31

I know how you feel trying to yank that thing out of the wall.  I discovered after that Home Depot, maybe Lowe's, sellls a Moen cartridge removal tool.  T-handled thing that screws back in place of the handle and plastic parts. The vacuum after shutting off the water makes it impossible to remove and I destroyed the old cartridge by grabbing it with visegrips.  By the way, in some models, the gears are used to set the maximum hot water mix so you don't get scalded which limit how far the handle is turned.  Definitely a multi-trip to the home center project.

vlcowley (author)caitlinsdad2010-08-22

If you plan on replacing your old cartridge, new Moen cartridges come with a little white plastic cap designed to help loosen the old cartridge for removal. Once you’ve removed the retaining clip, place this plastic cap over the old cartridge, give it a twist or two with an adjustable wrench and it should be fairly easy to pull the cartridge out. No special tool required.

caitlinsdad (author)vlcowley2010-08-23

I had the spare cartridge that I saved from a matching shower unit when that other bathroom got remodelled. I did have a refurbishing kit to replace the outside O-rings and some plumber's grease. Old house fixes are tough because you have to shut off the water main as you don't want to mess with the shutoff keyed valves that feed the shower mixer and they didn't install accessible shutoff valves back in the day. You have to take it out and match it at the store to get a new one.

dataphool (author)2010-02-01

Hear! Hear!  I found it very frustrating to find nothing on the net.  Except web site after web site wanting to sell me another valve.  Lacking any instructions, it is no wonder that it took me much longer to have a shower again than I wanted.  I will save your article for possible future use.  Thanks.

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Bio: Im an ex computer guy who turned locksmith then Resource Conservation Coordinator for a school district and I still love to tinker with everything. During ... More »
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