I was cleaning my water softener and it was full of a black sand-like substance. Searching the net and asking around at my local stores, no one was able to explain what this was.

I had a company come clean it 2 years ago and am not sure what they put in it...

Anyone have any clue of what this is?

Thanks!

Assume you are cleaning the brine tank of your water softener? If you use rock or commonly called crystal salt, it is mined. Whatever dirt, gravel, black stuff, is in the ground, comes out when you put it in your brine tank.
Solar salt is cleaner. Pellet salt is the cleanest but best if you have a platform in the bottom.
Retired... 30 yrs in softener service/sales
Rosharo

Assume you are cleaning the brine tank of your water softener? If you use rock or commonly called crystal salt, it is mined. Whatever dirt, gravel, black stuff, is in the ground, comes out when you put it in your brine tank.
Solar salt is cleaner. Pellet salt is the cleanest but best if you have a platform in the bottom.
Retired...30 yrs in softener service/sales
Rosharo

Thanks for the quick reply.