Potable water tank cleaning

[jefflance512]

Bought a RV second hand from someone that had less of a clue than I do about a year ago. My 1st RV.
BLUF: How do I thoroughly clean the black chunks out of my potable water tank?
I've recently started looking at the potable water tank and noticed that it looked like it had some black scaling on the inside.
I filled the tank put a cup of bleach, let it sit for several days, drained it down to about half, road it around for 30 min or so drained it, several chunks of the black substance came out, still see a good bit on the walls , took a larger clear hose sprayed water on the inside, used it to drain larger chunks.
When you touch the chunks that come out the dissolve.

 

[Phillbo]

Might be time to call in a pro and have all the tanks cleaned. Start fresh. Don't forget about the water lines. They need to be sanitized as well... be sure to run your bleach through them.

 

[MNC]

I don't know for sure but it could be black mold. the former owners might have left some water in for a long time

 

[jefflance512]

Bought a RV second hand from someone that had less of a clue than I do about a year ago. My 1st RV.
BLUF: How do I thoroughly clean the black chunks out of my potable water tank?
I've recently started looking at the potable water tank and noticed that it looked like it had some black scaling on the inside.
I filled the tank put a cup of bleach, let it sit for several days, drained it down to about half, road it around for 30 min or so drained it, several chunks of the black substance came out, still see a good bit on the walls , took a larger clear hose sprayed water on the inside, used it to drain larger chunks.
When you touch the chunks that come out the dissolve.

I have decided to replace the tank, no need for any other replies.
I don't think I would feel safe drinking even if someone cleaned it.
And probably cheaper with a self install