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Got it from Ace Hardware near me. They said it was chlorine. It had the smell of chlorine.

It was pumped out of a large holding tank.

I have never seen the effects of hydroxcide,but from what I have read and heard....it sure looks it. Good luck Dude......

I have been thinking about my problem so I should add this piece of information. I purchased my rig used from a guy who runs a business selling to contractors in the cleaning business. The roof chemical tank had a brown stain about 1/3 of the way up on the tank. I was told that a pesticide had been in the tank previously.

Could the stain be the residue of the pesticide? The dark stain in the tank disappeared once I had applied the roof mix.

I am going to make a small batch of roof mix and clean a small section to see if that will clean the stain.

always gotta clean a used tank out properly first.

Baltimore MD Roof Cleaning 410-482-4367 wrote:

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looks like it might have been hydroxide, what is the exact chemical name of what they sold you ??
It needs to be Sodium hypochlorite

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 Bill, even if it had been Sodium Hydroxide it would have rinsed the Roof off and not left that stain...Something weird is up.

Anyone think it's the pesticide that was on the tank as a stain? There was no liquid in tank when I made my mix. I still plan to clean a small section to see if the stain will come off.

As far as I know calcium hypochlorite is another chlorine used in pools and it would not have done that or really cleaned very effectively either. I wonder what was in that tank??
Also the container should say what the chemical is. If it does not you just learned a valuable lesson the hard way, never use chemicals that are unknown to you, especially in a mixing situation. Also it makes you stand apart from the guy who knows terms like simple green and purple power, but have no idea what caustic soda or ammonia are.
Larry has been cleaning roofs for a long time, and if he has never seen this either, it may be hard for us to help. Especially if you can't find out for sure, everything that was in that mix, from tank residue to the type of chlorine used.
It is so strange, it looks wet??
Can't try to neutralize it without knowing what it is.
Someone should go look at it, I would if I lived near wherever it is.

I've seen this before....... Apply another coat of Apple Sauce or Cider, which ever you prefer.
What has happened and it happened to me was the pesticide had adhered to the inner portion of the tank and I assume the brown stain you are referring to was that left where the level of fill ended.
This pesticide neutralized the chlorine or weakened it. Buy looking at the photos, my guess would be this roof is 12 to 13 years old and had never been cleaned. Therefore the algae had grown deep into the roof and the sauce had enough strength to penetrate it but not to eliminate it. Thus, dark staining.
My recommendation is to purchase a can of Iodized Salt pour it in the tank and fill with water. wait 15 to 30 minutes and drain it. Fill again with water and drain a second time. You should now be safe.

We make it a practice to flush and rinse our tanks monthly. If you check the bottom of your tanks every 30 days or so, you will find SH residue on the bottom. This residue can also destroy a pump, clog lines, etc.

Good luck. Let me know what happens.