Instruct: Classify an Amazon review into positive or negative sentiment.
Query: 5 failures in 5 years.

I've now been through 5 different units in slightly more than 5 years! Extremely poor reliability. One heating element failure, three printed circuit board component failures, most distressing! The units just won't last any length of time. I've spent a lot of time trouble shooting,talking to customer service reps and technicians and far too much time and money ripping out old failed units and putting in new ones. I remodeled the space and area when I put in the first one and don't have the space to put back in a tank style heater. It lasted 20+ years!