White flakes in hot tub.. is this calcium?

[125mph]

For the first time in 6 years, I have white flakes in my hot tub. I thought the plastic was coming off and I drained the tub last night. Turns out maybe its calcium deposits? Here's some pictures. Please confirm this is calcium!

And if so, do I just scrub with vinegar water and refill, making sure my PH is low instead of high?

[wmccall]

Welcome to the forum!  I've heard of white flakes being something else entirely that could be more serious.  I'll let someone else comment. When my PH has been off I will get a calcium deposit that feels more like grit than flakes, on my white spa surface.

[The Wizard of Spas]

I agree:  A "sandpaper" feeling generally tends to be the side effect of calcium deposits.  It could be something as benign as a build up of 6 years of usage in your lines that is finally purging itself from the system.  Regardless of if it is or not you may want to clean out the lines using a specialized product to purge the system. 

If it is a metal deposit as wmcall and myself have noted, citric acid (Vitamin C tablet, lemon/lime/orange wedge) would dissolve it.  You can do a quick test with the aforementioned products.  If not you'll need to report back to investigate further.

[125mph]

Great thank you!

I got a scrubber and did some gentle scrubbing.. It's coming right now. I'll fill it with new water and make sure the water chemistry is balanced.

Thanks!