Delta valve body leaks

[Jack H]

Hi, I just installed a Delta valve body and necessary tubing from hot and cold, tub spout and shower head. While pressure testing for leaks, I have the drop elbow plugged, Sharkbite cap on tub spout and the supplied test cap and bonnet ring screwed on. With water pressure turned on, no leaks, unless someone is taking a shower in the adjacent bathroom. Water drips out at the test cap and bonnet ring. What would cause this?

 

[Cwhyu2]

O-ring damaged on test cap.

 

[Sponsor]

 

[Jack H]

Hi, I just installed a Delta valve body and necessary tubing from hot and cold, tub spout and shower head. While pressure testing for leaks, I have the drop elbow plugged, Sharkbite cap on tub spout and the supplied test cap and bonnet ring screwed on. With water pressure turned on, no leaks, unless someone is taking a shower in the adjacent bathroom. Water drips out at the test cap and bonnet ring. What would cause this?

O-ring damaged on test cap.

 

[Jack H]

I thought maybe that but why does it leak only when adjacent shower is running?