My toilet fill valve leaks at the top only when the bowl is full.
Until the bowl is not full it is not leaking from the top.
This is a video of the leak:
https://vimeo.com/270998266
I want to decide whether I should only replace the cap
of the fill valve or the complete fill valve. I ask because the cap is 10 bucks cheaper. Should I replace the cap or the complete fill valve? Is there any test I can do to figure out this myself if this information is not sufficient to decide
Best Answer
Just the cap.
The most important part of the fill valve is the cap assembly and the valve it contains. The seal between the cap and the valve body may be compromised, and the seal is in the cap. There appears to be nothing wrong with the valve body or float assembly.
If you don't know how, you just shut off the water and, while holding the valve body with one hand to prevent bending and spinning, turn the cap assembly counter (anti)-clockwise and lift it off (pop the float rod loose from the float arm first).