I do not live in Denver but in the suburbs and use tap water for my growing. I found it's important to let the water settle for a day or two before using. I fill up my water containers and I do not use them for a few days. I do not add nutes to the water till I am going to use it.

There are some strains that seem to do better than others with the unfiltered water. I think some strains are just alittle pickier in regards to PH etc.

Hope this helps and good luck to you.

Happy growing.