Hello, new to the forums and in need of help. We have an add on garage bed and bath which the previous owner build. It has a dedicated electric water heater for this add on. It's a 30 gallon unit that keeps reseting the thermostat. I've tried removing the heating elements to replace but the hard water has sealed them shut. I was able to drain some sediment but not even close to all of it. The unit is from 1988. Should I replace with the same size unit or scale it down? The unit only provides water to sink in garage and upstairs bathroom I feel this is overkill. I'm open to all suggestions