[DoubleF]

Originally Posted by Paulie Walnuts

So just get a kit like this with the adapter and handle like this as timun posted?

https://www.homedepot.ca/product/moe...5549?rrec=true

This is what happens to the plastic handle each time I've put one in it snaps.

https://postimg.cc/nscRrWD6

In theory, yes. But maybe a step back is required.

I recall a plumber using some type of clamp to test the valve before installing the handle. What happens when you try turning on the water? If it seizes or is stuck, or somehow is reversed, maybe it's not purely an issue with the plastic piece. Any new one might snap as well due to the resistance from the valve inside that the plastic is not designed to sustain? It should turn relatively easily even without a handle.

EDIT: Now that I look at that pic, I had those shower handles. They were solid as F. But the plumber guy had to replace them when I got pressure values because they were not designed to be used with the pressure values he installed. Posi-temp adapters are a type of thermostatic or pressure valve.

Is this possibly a situation with an incompatible handle and valve? I don't recall if there was an extra piece inside, but they were hard enough that they shouldn't crack easily when turned. How much pressure did you use when turning? Shouldn't it turn easily?