I'm sorry... I used the wrong terminology... I should have said galvanized pipe, as below.I have been in the plumbing business for over 55 years and have never seen castiron water lines.
Had another plumber out. The pipes are clear. He said he hadn't seen stems like that before in multiple sections but these looked like the American Standard stems in the rebuild kit. He suggested buying the rebuild kit along with the manifold in case the stems didn't fit the existing one.So... the OP says that the water is at a "trickle"... and maybe this has something to do with washers and seats... although that's not been my experience... even if a washer comes loose inside the valve, if you open things up enough, water starts to flow.
I notice that you have a picture of your sink as well. Is it slow, too? How old is the plumbing and what is it made of? I've got 60 year old cast iron pipes in my house, and while the cold water in the shower is OK, the hot water really is a trickle, all due to the corrosion and closing off of the pipes. All piping is going to be replaced within the next thirty days along with my bathroom remodel.
So... my question to you is: What is the flow like if you pull out the valve stems and turn on the water so that it squirts into the tub? About what you'd expect? DId it clear any grunge that might be backed up in the valves? And not to belabor the point, what's the chance that your tub spout and shower head are simply full of debris that is blocking the flow. Obviously, if there is no strainer on the tub spout, this is a non-starter.
That's the trick, finding a plumber that know the older fixtures. The last plumber suggested buying a replacement manifold along with the rebuild kit for the aquaseal in case the stems don't fit the old one. Haven't been able to find the replacement manifold though. Apparently discontinued.Not every plumber has worked on every fixture out there. Some think like you said, what will happen if this is all tore apart and wont go back together correctly. Then they are on the hook for getting your 60 year old faucet repaired and operating correctly. The smart move for them is to tell you to replace with something they are more comfortable installing. I have been in this industry for a lot of years and i know i haven't worked on everything, just like lots of plumbers haven't done things i have.
You need to find a guy or company that is experienced in working on and repairing older fixtures like you have. Good luck to you and i hope your able to salvage the fixtures your mother prefers.
if you stick with american standard to change the seats and stems is probably 1 hour tops and the parts are inexpensive....go to a plumbing supply house...or two...inquire about the plumbers who come in tell them what your dealing with ....you will probably find someone,like mentioned before ask for someone familiar with older fixturesThat's the trick, finding a plumber that know the older fixtures. The last plumber suggested buying a replacement manifold along with the rebuild kit for the aquaseal in case the stems don't fit the old one. Haven't been able to find the replacement manifold though. Apparently discontinued.
Someone else mentioned a chrome seating that could be rough and cause further problems down the road. The last plumber although he said to go ahead and get the rebuild kit was obviously unfamiliar with the stems.
I have found a Pfister with a star shaped handle that would be close enough if we replace the whole thing but, this guy seems to insist on Moen or Delta.
After three plumbers I still have no clear path forward.
And, it's my wife, not mother