I bleed the raditaors on my old hot water sytem and after several weeks the air returns and it is very noisy. Any ideas as to what the problem is. The air is coming in from somewhere???Thank you Guy

I'm considering going to a tankless system but I'm a starving for information on energy savings in a low volume environment. All of the calculators out there and articles seem to reference to quite high loads on the tankless system and the very reason I'm considering tankless is because our household is the opposite. Me and my girlfriend live in a home in a temperate area (Vancouver, BC, Avg summer tmp 17-30 deg C, Avg fall/spring temp 8-15 deg C, Avg winter tmp 0-10 dec C, freezing and snow are rare). We only use hot water for - Showers and occasional bath (one bath every three weeks or less, mostly take showers) - Dishwasher - Hand operations (handwashing, dishes, misc) I havent done any official tests but excl the shower we probably use about an average of 3 gallons of hot water per day. A 15 minute shower with a low flow head at 1.0gal would be another 15 gallons so lets say an average of 20 gal/day of hot water. Our water heater is pretty efficient and uses natural gas. I'm thinking a small single function (we never do multiple anyway) tankless running electric. While the electric costs more per BTU than natural gas I'm thinking the savings must be there because we have a 80 gallon hot water tank and the only time it's ever run out is when we've both been sick or something and wanted to take baths one after another which is something that probably only happens once every few years. All of the calculators are based on 60-80 gals of hot water usage per day, this is way more than we use and they all seem to indicate 30% savings at that level, I'm thinking at very low use the savings would be higher?