Which bathroom fixtures are most resistent to this problem?

As I understand it, when you swivel the knob to control the mixture of hot and cold water in your shower or bathtub, there's a mechanism in there that is susceptible to wear and the build-up of minerals because of the water running through it. Since people tend to always take showers or baths within a certain narrow range of temperatures, this mechanism wears/accrues mineral build-up unevenly. After a while you have to keep changing your knob position to get the same temperature.

I've heard you're supposed to mitigate this problem and "exercise" the fixture by turning it all the way hot and all the way cold for a minute before adjusting to your desired temperature. I'm guessing almost nobody does this.

Is my understanding correct so far? And if so, is there a type of fixture that is designed to eliminate this problem? How does it work?

3 Types of Shower Diverter Valves Explained

While there may seem to be a wide variety of shower diverter valves, there are only 3 main types of these useful devices. If you have visited a friend's house or hotel, you might have noticed all the different kinds of shower diverter valves. The shower diverter valve can be located between the faucet and the spout, it can form the center of the faucet or it can be a vertical pull arm on the tub spout itself.

Why Shower Diverter Valves Are Useful
The shower diverter valve enables the shower to be installed over the tub, eliminating the need for a separate shower stall or enclosure. This saves space in the bathroom avoiding the installation of extra piping, faucets, and tiling. A rubber washer is usually responsible for cutting off the water flow to the tub and forcing it vertically through the shower head instead.


3-Valve Diverter
This type of diverter, located between the taps on a two-tap faucet, can bring water to both the shower and the tub. The hot and cold water taps are turned on to mix the water to the correct temperature. Usually, turning the diverter clockwise 180º allows the properly mixed water to flow out through the shower head. Turning the diverter counter-clockwise will return the water flow to the tub.

Two-Valve Diverter
As in the 3-valve diverter, the bather runs water through the tub spout until it is blended to the desired temperature. The diverter, with 2 valves each in the shape of an L, pushes the water upward to the shower arm and out the shower head. This 2-valve diverter can be located in the center of a faucet that adjusts temperature with a single dial turned to the left for hot water and to the right for cold, or it can be set between the taps of a 2-tap faucet.

Tee Diverter
The tee diverter is a single-valve diverter, located in the tub spout. The bather runs the water to the temperature he or she prefers, and then pulls up the diverter pull arm in the tub spout. The water then comes out the shower head.

How to Properly Deactivate a Shower Diverter
Depending on the style of tub faucet you purchase, you may get any of these 3 types of shower diverter valve. All are equally effective at keeping the water directed through the shower head until you release them. It is always best to release the diverter and allow water to return to flow through the tub spout for a few seconds before shutting off the water. This reduces strain and wear on the diverter valves.
If you encounter a shower diverter and you aren't sure how it works, make sure you start the water while standing outside the shower to ensure you don't get scalded by hot water. If you have a shower that has water flowing from both the tub and shower, you may need to clean or replace your diverter valve.

too answer your question, use a valve that has a ceramic disk instead of rubber washers

Frodo, I think he was talking about anti-scald??????

Your understanding is correct, the modern valves are code compliant, and because they are, I've not attempted to subvert them, though there are more than likely those that have.