I HAVE PUT PVC IN LAKE AND FOUND SOME IN IT ALSO ,I CAN SEE IT ON MY UNITS,859 AND 1199,I SAW IT WHEN I FIRST PUT IT DOWN,SAW IT A WEEK LATER AND SAW IT A MONTH LATER AND SAW IT PASS WEEK,DID NOT TRAP AIR IN IT ,NO ALGAE ON IT,AND DID NOT SCRATCH IT UP,IT IS A MATTER OF SETTING YOUR UNIT UP RIGHT TO SEE IT,HOWEVER YOU DO NOT NEED TO SEE IT IF YOU KNOW WHERE IT IS ,JUST SEE FISH AND IF NO FISH ,KEEP GOING