How to clean hard water spots and weird stuff in carboy?

[JoppaFarms]

Hey folks. I recently got a few carboys off Craigslist and I'm trying to clean them up. The guy said they hadn't been used in awhile so I figured a good soak would do the trick. Well after about 3 Oxyclean soaks and scrubbing with a brush they still look like this. When the liquid inside starts to dry I get this weird streaking pattern where the moisture always collects. Same pattern every time. Any one have any tips on getting rid of this so I know I have a clean fermenter?

 

[kombat]

Are you sure they're not hairline cracks?

 

[Garybeer]

I would try to soak it with white vinegar for two days and see if that helps, I've done that before with hard water spots and it worked better than commercial cleaners.

 

[JoppaFarms]

Are you sure they're not hairline cracks?

I'm not sure, no. I had it filled completely earlier and it wasn't leaking. They seem awful wide streaks (probably 3-4mm) to be hairline cracks.

As for the vinegar...I don't have 6.5 gallons of that stuff haha. Will a cup or so sloshed around do the trick?

Also, does it even matter? If I run sanitizer through, it should be ok, right?

 

[day_trippr]

[...]As for the vinegar...I don't have 6.5 gallons of that stuff haha. Will a cup or so sloshed around do the trick?[...]

Yes, that will be fine...

Cheers!

 

[Beernik]

I second the vinegar idea. I use it in my dishwasher to keep hard water spots off my glasses.