Its the balancing spool and yes you can replace it if you are reasonably mechanicly inclined. Part number RP19804
In our secondary bathroom, our shower/tub has a single handle knob and when turned to HOT no hot water comes out at all and it just shuts off the water (it drips just a little bit when on full HOT, and that water is also NOT HOT). It is a condo unit and it used to work just fine and this particular shower has seen very little and infrequent use. All other faucets work perfectly fine in the condo.
What do you think the problem is and how can I fix it myself? Thank you for any and all help!
Do you have a plumbing shop in your area that deals with DIYers? These guys are knowledgeable about the products and are very willing and able to show you what to do. You may occasionally find a "smock man" that can do this, but usually at a Box store you just find sales people. Actually, once the cover plate is removed, you should be able to pretty well figure out what to do next.
You may find it very easy to turn a small job into a big one...
There is a nut that holds the cartridge in that if it is hard to remove and you twist too hard you can ruin the valve.
Yes, yes you can...
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