I installed a shower valve I installed a custom mortar shower pan (pvc liner with plastic vapor barrier behind the walls) I installed cement boards on the wall
the area on the front of the cement board around the shower valve, a diagonal line (as if water was dripping down) going to floor and a larger area of the mortar pan in front of the drain are mysteriously wet. When I removed the cement board the back of the cement board was dry (however in between the pvc liner and the plastic was wet also some of the studs were moist) all the copper pipe, joints, and shower valve appear to be dry.
What is causing the moisture? can it be evaporation from the drain? condensation?
What can I do to fix this?