Steve,
Based on your last precautionary statement, I will add the "rule of thumb" for mixing caustics or acids with water. ALWAYS, add the caustic or acid to the water, never the reverse. IF the water is already there when the chemical is added, it will instantly be diluted and will not result in a violent reaction (erruption). Water first; chemical second.
Even when cleaning your home drains, never pour the chemical in a dry drain, then add water. ALWAYS run water first, then add the chemical.
Verne