So I cooked some corned beef yesterday in a zip log bag around 170, and after a few hours I could see the water start “foaming” up. after cooking, there was white chalky type sunstance on the machine and around the pot i cooked it in. I dupmped the water from the pot and just left it overnight and this morning i see it covered in this chalk substance. Could this be coming from the ziplock? is it not safe to use a ziplock?
Are you using a sandwich bag or a freezer bag? Really not advisable to use a sandwich bag. The material is marginally thicker than cling wrap. You really want to use freezer bags as the plastic is durable enough to be reliable for sous-vide.
Also, hard water will leave hard water scale on your container and precision cooker. Get in the habit of cleaning this up after every use (this is where having access to soft water would be highly advisable) 
Thanks. Never thought of that. I got ziplock “storage” 1 gallon bags. Guessing those are not the same as freezer bags.
Check the thickness of the plastic on them - they may be fine (but, you really shouldn’t be having any issues with the thicker ziploc bags - I know I don’t). You’re also only using them once, right?
Again, I’m buying the freezer bags as I know the plastic is thicker.