Plumbing Mystery

Bathtub had no hot water. Plumber came in and replaced the cartridge. Now no cold water. Replaced the limiting baffle. Now no hot water. BUT if he removes the cartridge and the limiting baffle and uses the little screw to turn on the water he gets scalding hot. But it does not seem to mix, despite a new limiting baffle and new cartridge. Does could this happen? What could be the cause?

Somehow, this thread is appearing twice … and I’m reporting it as such …

Sounds like you have an American standard or Kohler style valve with a separate control cartridge and pressure balance assembly. Make sure they are installed correctly. They can be installed upside down which messes up the flow like you describe.

Got a picture of the valve without the trim on it or just the cartridge?

An old water heater can disintegrate and send particles into the pipes. And old rusting metal pipes will release particles into the pipes.

A city water main can also release particles into your pipes.

These particles will clog valves!

To fix this, remove the entire valve and connect the spout/shower head connection to a water hose so water flows backwards in the valve. Alternate turning on the hot and cold. This is called "back flushing.

This can also be done with the valve still installed, but the water needs to able to flow backwards out another open valve (one which will not clog when the particles reach it). And there needs to be hot and cold open valves.

Many plumbers DO NOT KNOW HOW TO DO THIS! They do however know how to replace the entire valve assembly and charge you a fortune.

To fix this permanently, install a whole house “screen” spin down filter like this…
https://www.amazon.com/Separator-Sediment-Filter-Additional-Replacement/dp/B00G01YH8E

You can periodically open the drain at the bottom to remove particles. And this will filter out particles coming fron the city water main.

If you have old metal pipes, you can replace the pipes in the house or just replace the pipes in the bathroom, but install spin down filters where the new pipes begin. (One for hot, one for cold.) Be sure the spin down filter is rated for hot water!

If the water heater is disintegrating, replace it… But before connecting, back flush all the hot water pipes at each faucet.

Notes: If you have ever cleaned out a faucet “aerator” and seen particles in it, those are the particles which will clog faucets.

New water saving faucets have small openings which clog much easier than old faucets.

Doing the above will also keep the little bowl refill water tube working in toilets as no particles will get through to clog it!

Moderator Note

The other copy (which did not have any replies yet) has been wished away to the cornfield.

Every plumber knows how to do that. If you are taking the time and effort to remove a faulty or clogged cartridge, you replace it. At $110/hr it is bad practice to spend half an hour trying to disassemble and clean out a part designed to wear and be replaced.

Once you have the cartridge out you flush the line and reinstall.

Is this a plumber or a “plumber?”

Thanks for removing the repeat post, my bad.

Eventually the plumber came to me with a small curvilinear piece of metal that had been causing all the problems. Everything works now. Evidently, despite the fact he said he had no idea what could be causing the problem he did suspect and just did not want to take the time to try to explain it to me. At $110/hr this was likely a nice thing to do.

But none of that will cause the problems listed in the OP.