My heater has worked flawlessly for 8 years (warranted for 6yrs) and last week it started running out of hot water towards the end of one shower. It's always lasted for 2 or more long showers. It's been a number of years (yeah, I know) since it was last drained of sediment, but it has worked so well I didn't bother. Could this cause this problem? geoforce6@comcast.net