You will find solutions available on smaller glycol chillers, with internal h2o tank, for ease of use. Water can be used to chill all the way down to seven°C but then glycol have to be added to chill further more. We use propylene glycol, a non-toxic alternative to ethylene glycol, https://bookmarkfly.com/story20229243/glycol-chillers-things-to-know-before-you-buy