[kramerog]

After soaking the fermenters in PBW solution and emptying out the yeast and hops, I'm left with a very pale yellowish "ring around the collar" immediately above the beer level.  I'm able to remove the ring with a spray wand, but it is hard to see if any of it is left behind.  Is the ring around the collar hop oils?  How important is it to remove it? RDWHAHB? 

[denny]

I don't think I'd worry about it.

[bluesman]

I don't think I'd worry about it.

+1

This is a common condition that occurs from the krausen scum layer staining the fermenter.
I haven't experienced any problems from it.

I wash the fermenters with a mild soap and hot water after each use and then sanitize prior to the next fermentation. This practice has not let me down yet.  If the fermenter becomes grossly stained, I would replace it.

[kramerog]

This is a common condition that occurs from the krausen scum layer staining the fermenter.
I haven't experienced any problems from it.

I used to think it was a stain, but it is a thin layer that I can see peeling off under the force of a spray wand.  I'm inclined not to worry about it as I have brewed a long time without worrying about it.

[euge]

After soaking the fermenters in PBW solution and emptying out the yeast and hops, I'm left with a very pale yellowish "ring around the collar" immediately above the beer level.  I'm able to remove the ring with a spray wand, but it is hard to see if any of it is left behind.  Is the ring around the collar hop oils?  How important is it to remove it? RDWHAHB? 

I'm assuming they're plastic buckets. Mine have been stained yellowish for a while now- they get that way after the first fermentation. I use oxyclean and a soft cheese cloth type material to remove any left over particulate. The hardest part is the "ring". Otherwise nothing to worry about as long as it is clean and replacing isn't necessary unless the plastic is deeply scratched or damaged somehow.

I think it's the hop oils and the acidic environment causing it. Presumably, the more hops one uses the worse it gets. RDWHAHB

[Mikey]

A chlorine bleach solution will get it out.

[Kit B]

If you're talking about glass fermenters, use CLR & hot water...Soak overnight...Rinse well & it should be gone.
I run into this fairly often.