"Mineral spirits" will work better but is more expensive and is not worth it for this application.Wear respirators with organic vapor cartridges, I recommend half-face 3M 6000-7000 series with 3M 6001 cartridges.

It has 5 filters & I sleeve the filter cartridges with white drain pipe stocking (Drain-Sleeve) to absorb the oils/residues etc so I have only replaced the filters 2x since new.

The envelopes are printed this way too.If you do that, make sure you buy one with each color in a separate cartridge.

Turn off the water to the house, then remove the shower knob and work your way down to the cartridge, which screws into the valve housing.

I also recommend using a blue pen but that is just my preference.Full disclosure, I dont't do wholesaling so have not actually tried this but it should work.PS  if you have never tried it, I refill my own ink cartridges at home. costs less then $5 and  takes less then 5 mnts. from start to finish.

I have the half-face respirator with the charcoal and the potassium permanganate cartridges but always try to find a safer alternative.

There was a cracked shower cartridge in one of the showers. 35 dollars for the cartridge, 50 dollars for the plumber and I closed at 300k.

You should be able to replace the innards of a toilet, change the wax ring, change all the plumbing under a sink (supply lines, shut off valves, p trap and other pipes) and above a sink (faucet and cartridges), replace the agitator dogs of a washer, replace the heating element of an electric dryer, change the air filter of your central air, replace the ignitor of a gas furnace, replace heating elements of an electric furnace, replace the ballast of a fluorescent light, the list goes on if you want to make more money in rental property near you.

If it's both sides then it could be the cartridge in the handle(s), or the shower head is gunked up.

Make it look all pretty and think of your runs,,manifold if needed and each faucet has own run AND shut offHere it was needed cause it was throwing lots of rust and grit into aerators and cartridges as well as the old interfered in  NEW electrical box install (AND every scrap of wire inside the house,,,,anywhere(That was a bigger project but very doable and much less expensive than a pro install.  )  MY electrician says he doesnt like to run new wire in old houses as it takes too much time and that job does not require a rocket scientist therefore he says you get the wires run I will hook them up.