If it is a dripping faucet, I would try to replace the cartridges first.

The other really nice thing about it is that the remanufactured ink cartridges on eBay are like 1 buck or 2 a piece.  

While doing the pre purchase walk some plastic cartridges were found in the cabinets.

Just didn't know if it was OK to install the cartridge sooner (before tilework was done) to avoid having the water mixing.

The bathroom in our rental has a cartridge that you push in to change from a shower to a bath, and the shower has a hose that lets you detach it from the wall. 

Yes, 7 times.Whenever possible, we use locks my team knows how to personally change (my favourite type are the ones where we can swap out the full cartridge for another).

At this point, I also learned that some cartridges in bath/shower fixtures are designed to keep the temp at safe levels to prevent scalding.

The unit is in awful condition, likely because there are too many people living in the 2-bedroom unit (at least 3 adults and 4 children), and their lifestyle habits have caused them to break something almost weekly (shower mixing valve cartridge, rails, cabinets, stairs, etc.).  

If you are doing a cartridge filter you don't have to worry about it.As far as the granite grip, it was applied right to the edge of the fiberglass.  

On a warmer day a few days after the subzero temps, the shower cartridge/valve (temp control and turn on thingy) broke, (on our rental side) that is when we shut of the water at the main to fix it.