Originally Posted By: IzzyJG99
Originally Posted By: adam2
These posts could be a reason to retain a conventional hot water tank since this is a potential emergency source of water.

An alternative sometimes proposed is an on demand water heater, these have their merits but have the decided drawback that they are not a standby store of water.


My friend, a plumber, tells people to put them in...only when they're doing total remodel or new construction where the unit can be installed as close as possible to the bathroom or dishwasher. They tend to lose more than the average ten degrees to tap that stand alone conventional tank heaters are known for. I looked at a few houses when I was looking for a place to live, that had them. All of them had a pressure control valve that slowed the water pressure down long enough to make it get heated. Where my house is at right now I COULD probably put in a On Demand unit. It's under the stairs, on an exterior wall. Problem is I doubt the city is going to plumb gas to just one customer. And having a nice cache of water in a tank in your house at all times is a plus for me. So I might leave it be.


The argument for on demand heaters is, IIRC, that no energy is wasted keeping 40 gallons of water hot during the 23 hours and 45 minutes per day that it is not needed. You could install the on demand device, and a plumb a holding tank into the cold water supply line before the heater. It would be a constantly renewed back up supply in case of loss of water service. You could pressurize the holding tank with an air compressor and preserve water pressure, too. And probably run the on demand heater on propane, to avoid NG installation expense.
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