Backstory:

I had to adjust the water temp limit on my temptrol in one of my bathrooms and of course the cap was rusty and fell apart when I pried it off. I designed and 3d printed a replacement cap. In the photos you can see the plastic part in the cover photo compared to the stock plug in the second photo.

Print Settings:

I suggest PETG since it needs to be flexible I did 0.15 mm layers, but you might even want to go to 0.1 mm. Supports from the build plate are a must unfortunately, I didn't see an easy way around them without printing it upside down which would make the flat top and not rounded.