You have to separate what you KNOW from what you THINK.
Our usual glue procedure for PVC conduit does not make for a waterproof joint. We're electricians, not plumbers, so we don't worry about water entry.
This is because water can / does enter the pipe from many other sources ... condensation, boxes, etc.
Pipe should be "arranged to drain." This might involve even putting a weep hole in the side of the pipe at a low spot. Or, replacing that LB with a Tee, for a drain to direct the water whare it won't harm anything.
Mike raised a good point .. are you sure the water is in the pipe, and not just following the pipe through the wall? That is one area that might benefit from some manner of sealing.
