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.

Comments

[tosenbach]

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]

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]

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]

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]

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]

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.