So I have been using a pair of plastic inductor tanks for over a year now with no issues until fairly recently. I've have a few batches in one develop some sort of infection, its either lacto or aceto as it sours the beer. My starters are 4L normally so the yeast beats it out, cold crashing and cold storage seems to slow whatever it is down enough that it doesn't ruin the beer. I left a batch on for several months in secondary and of course it has affected it quite a lot more, its a dumper. I use a 2400 GPH pump with a stainless spray ball to clean with hot PBW (bucket with 1500w element and the pump) to recirc through the tank, I let it run for over an hour, so its pretty darn clean. I rinse a few times, using the pump again. Then I run star san recirc for over an hour. The spray ball does a good job, very good coverage top, sides, etc. My fear is the bugs are in the racking cane, so I may take that off and just boil it. I'm considering chlorine, caustic, acid, flame thrower.. Just can't seem to kill it, and I've soaked the whole thing in star san overnight to try and kill it.