Faster Melting Filtered Water

I recently purchased a new filtered water picture which is claimed to filter out all added chemicals to tap water (i.e Cl, F ). I've noticed that the filtered water appears to make my ice (which is made from the same tap water, but not filtered) melt faster than in unfiltered tap water or even bottled water. Any thoughts as to why?
- Jim (age 23)
Texas

We have many old answers on melting rates of water with and without impurities. Unfortunately, they don't really explain what you saw. So the question becomes what experiments can you do to test some ideas.

Maybe the filtered water gets warmed up a little as it goes through the filter. You could take a glass of it and of tap water and let them sit next to each other for a few hours before adding ice cubes. Maybe then the melting rates will be close to equal. If not, follow up and we'll try to think of other experiments.

Mike W. 

(published on 05/15/2015)