Used 1000 litre Containers

I was prowling the local classified ads the other day and I found someone who is selling 1000L plastic tanks at a very reasonable price. I have been keeping my eye out for some of these to create a rain water collection system for watering my garden and for a thermal battery on my greenhouse that I am building. He said that they were used to store silicone and glue. Can any of the experts on here weigh in and let me know if they would be safe to use?
Thank you for your time.
Regards
Brayden

In my area you can buy normal IBC totes or food grade ones.  The latter had food ingredients in them.  I would only get food grade ones.  Even if it was for a thermal mass in a greenhouse, you may want to drain it some day and where do you put 1000 liters of possibly contaminated water?

Thanks Mike. That is what I am leaning towards thinking but I want to hear from more knowledgeable people than myself. He told me that they have been rinsed out but would that really clean them?  Does the plastic hold the chemicals?  Enquiring minds want to know.

Regards
Brayden

Brayden Plummer wrote: Does the plastic hold the chemicals?

I am often surprised by how well plastic absorbs things. I know someone, for example, who smokes in her house, and whenever she gives me something in a plastic bag (the type from stores), the bag reeks of cigarette smoke, even days or weeks later. So, yes, I would say that plastic definitely holds chemicals.

I wouldn't touch em for drinking water.

I've gotten IBCs that were 'rinsed out well', and... it was a multi-hour process to get them actually kind of clean. Rice syrup residue... Residue absorbed into the plastic seems like it would be a long slow leaching process.

Depending on the design and price I might grab them to use the cages for any number of things, passing the plastic parts on to someone braver or stupider... if they seemed REALLY clean and odorless, I might use them for non-potable stuff. Maybe.

I passed on them.  Thank you everyone for the input.

Regards
Brayden