jac,

Flint River Ranch uses tocopherols, a natural antioxidant and Vitamin E source, and human-quality ingredients to slow the oxidation process of fats and oils to ensure its premium pet food products remain fresh as in their initial state. Vitamin E is an antioxidant that retards the oxidation of other vitamins.

Doesn't sound bad to me. If you are concerned have the water tested and see if the concentration of these additives are at problem levels. I doubt it. JMHO Aloha

That's what I was thinking, it says on the side of the tank, Food Grade. My concern was the oil possibly locking up the mineral ion's but I'm not a chemist and not sure how it bonds with other elements. I never thought about getting a water analysis, that's a good idea and will be my next step, thanks.

jac,

Just a thought. The concentration of the oils at this point, if you used a de-greaser to clean it, would be too low to react with anything. You would see an oil sheen on the water if the oil was in high enough concentration. What minerals would you be worried about locking up? JMHO Aloha

If I were faced with this problem, I would contact your State Cooperative Extension Service and get referrals to their specialists. This has always worked well for me. Additionally, I would contact your State university, specifically the specialists who have knowledge about Farming, Cattle, Watering livestock, etc. I have contacted many who were overjoyed in being able to put some of their knowledge into practice. A followup to their Chemist would be worth the call.