Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Water purifier

Easy to install. Seems to work as expected but hard to gauge since there is no way to check the purity of the water coming out of the tap or filter. Would be nice if they built in a way to measure when to change the filter rather than just providing a label to write the date on. Don't understand why the price goes up significantly every time I buy this. It will soon price itself out of my budget.