How to fix leaky Moen Karis bath faucet (from Costco)

I purchased Moen Karis (84346SRN) single handle bathroom faucet back in 2022 from Costco. I installed it around Spring 2022. It started leaking after about 1.5 years. I'm sharing in this blog my experience fixing this leak and I believe the process is similar to most single handle bathroom faucets. 

Moen's warrants their faucets will be leak free to the original purchaser for as long as you remain the home owner: "If this faucet should ever develop a leak or drip during the Warranty Period, Moen will FREE OF CHARGE provide the parts necessary to put the faucet back in good working condition and will replace FREE OF CHARGE any part or finish that proves defective in material and manufacturing workmanship, under normal installation, use and service".

I contacted Moen via this form and sure enough they promptly shipped this replacement cartridge kit which the part is confusingly labeled as "202233 Screw kit" in their website. 

202233 Screw kit (cartridge replacement)

Notice the form requires uploading a picture so I provided this picture of the leak:

Leaky faucet

Steps to replace the 202233 cartridge on Karis faucet

Step 1: first start by closing the hot and cold water intake.

Step 2: next, use the provided Allen key to unscrew the bolt from the back of the faucet.

Step 2: unscrew bolt from back of faucet

Step 3: once the screw comes out, just pull the faucet handle upwards.

Step 3: pull faucet handle up

Step 4: you will see that there is a plastic cover part around the faucet (with a chrome finish). This is merely decorative, but it needs to be removed. This part just pops out, if it doesn't come out try turning it around and wiggle it until it comes out.

Step 4: remove plastic cover

Step 5: remove the black plastic nut. This turned out to be most difficult task. I first tried the installation part that comes with the faucet and I still had lying around. This is supposedly "Moen Installation tool 118305", but it's just not large enough. Even in the questions and answers, Moen Plus Support answered this is 13/16" on the large end. It needs to be 7/8" instead, which Moen confirmed after I contacted them.

Step 5: remove nut - attempt 1 - using Moen installation tool 118305

My second attempt was to use a regular 7/8" wrench but there is just not enough room horizontally to grab the nut.

Step 5: remove nut - attempt 2 - using 7/8" wrench

My 3rd attempt was to use a regular adjustable wrench, but had same results, not enough room horizontally and the wrench was too wide to try it vertically.

Step 5: remove nut - attempt 3 - using adjustable wrench

I dit not have a 7/8" socket to try, but I knew a regular socket would be too wide to fit. I headed to my local Ace Hardware store and they suggested trying this "Tub & Sower Valve Wrench Set". It comes with one that was 29/32" which I thought would be close enough, but it ended up being too large to fit in (luckily I was able to return this).

Step 5: remove nut - attempt 4 - using 29/32" snug socket

I was about to give up and I reached out to Moen and they kept insisting that any 7/8" wrench would work. I searched for "snug 7/8" wrench/socket" in Amazon and came up with this "Amazon Basics plumbing adjustable wrench" that I thought was worth a try. I first tried horizontally and no movement at all... but then I tried vertically (as shown in the picture) and voila! The nut finally came out very easily.

Step 5: remove nut - success with Amazon Basics plumbing adjustable wrench

Step 6: remove cartridge by pulling it out

Step 7: install the new cartridge. Just need to align the openings.

Step 8: install the plastic black nut. It's always a good idea to apply silicone grease around it. Use the same plumbing wrench to tighten it.

Step 9: replace the chrome plastic cover - almost forgot about this one!

Step 10: replace the faucet handle.

Step 11: put back the bolt using the Allen key.

Step 12: reopen the water supply and test it. In my case the leak was completely gone!

Here is a time lapse video showing the whole replacement process: