Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Not for untreated well water!

If you are using this for well water, please note that right on the packaging when you get it- in the left hand front bottom corner- that it should not be used for untreated well water. I am not sure what else you would use if for. I used this filter years ago when our well was new and I do not remember there being such a warning.One might want to go to the 10 micron or finer size for well water and expect to change it more. I use the 10 micron filter from the same company and like them very much over the years. The 4.5 micron is also good but requires frequent replacement when a well is new or there is a lot of rain.I was hoping to use this as we just put in a new well pump and there is a lot more sludge in a new installation, but I am hesitant to use it now due to the explicit warning.