We have a leaking bathtub faucet and need to replace the cartridge but we cant’t figure out how to remove the casing (estachian?) around it. I don’t know the brand or model number. Everything is stuck from the hard water. We’ve already replaced the faucet but that didn’t fix it. Any help is much appreciated!!
The stem is held in place by a u-shaped piece of metal. If you scrape through enough crud, you'll find the bottom of it on the outside of the metal cylinder. Pull it out with a pair of pliers. https://www.youtube.com/watch?v=ZkZad_sHQkQ about 0:50 in is what I'm talking about.