We installed an ISE instant hot water heater last June. It failed in
October. The serviceman said the tank of this top of the line model was made
of plastic (a worry), and this model was known to have problems. They
replaced the whole unit, within warrantee. I suspect it is an engineering
design fault, and will fail again, and ISE will eventually return to st.
steel tanks. We have had good luck with ISE garbage disposals, tho.
Like other posters, I would suspect that your water may be corrosive. Our
last house had a 12-15 year old ISE water heater under the sink, and it
worked fine for the 3 additional years we lived there.