Black sediment in the bottom of commercial chlorine tank

[jamescox]

I just bought a chlorine tank that I filled with commercial bleach. The tank was clean and brand new when I filled it, however now that I've dispensed all the chlorine, I've noticed this brown and black sediment at the bottom of the tank.

Is this a normal biproduct of bleach instability? Or could I have gotten dirty chlorine? It was brown when I got it and my K-1579 test kit showed 12.5%, but it was yellow and around 11% by the time the tank was empty.

 

[JamesW]

Maybe iron.

Try a magnet to see if it attracts the dirt.

 

[jamescox]

Maybe iron.

Try a magnet to see if it attracts the dirt.

It doesn't appear to be iron. But now you have me thinking. I'm going to go back to the tower it was dispensed from and look at the setup. I want to say it was all HDPE and sch 80 PVC but I'm not sure

 

[JamesW]

Maybe some sort of sand?

 

[jamescox]

Maybe some sort of sand?

When I went out to check it with a magnet, I had to use a flashlight and I got a better look at it. It actually does look like fine sand mad of black, gray, brown, white and tan particles. I scooped some out and squeezed it between my (gloved) fingers and it acted like a paste

 

[JamesW]

Ok, some sort of contaminant, but unsure what it is.