With the advent of so much home plumbing being of plastic, a coil of PVC tube in a regular countertop microwave oven could produce quite a bit of hot water. It may even heat up faster than the apartment hot water with which I'm all too familiar.

Would a countertop unit provide the consistant and controllable temperature that would save time and money under regular use?
-- reensure, Dec 09 2000

Probably not efficient enough. There's substantial losses making microwaves from wall current, and not all of them are absorbed. You can heat water pretty fast with a conventional heating element and a large surface area. A "demand heater" is a heat exchange pipe with a resistive heater: cold water goes into one end and hot comes out the other. This actually makes a lot of sense, as you are not keeping a big tank warm all day, though gas is probably cheaper per BTU in the long run. Demand heaters are pretty much standard in Europe, though they tend to produce pretty wimpy showers.
-- rmutt, Dec 09 2000


There are gas 'on-demand' water heaters. They <the heaters in general> put out about 3 gallons per minute of hot water. Most people don't use straight hot water, and most modern US showerheads are restricted to 2 gpm or so, so they work pretty well...Me, I intend to put one in each area where they might be necessary, to cut down on water pipe and waste. All the water between the heater and the faucet is dumped down the drain until the hot water reaches.
-- StarChaser, Dec 09 2000


How about combining an electric "on demand" heater near demand locations (e.g. bathrooms) with a centrally-located 'conventional' gas water heater? The electric heater would provide hot water immediately and yet most water would be heated inexpensively by the gas-fired heater,
-- supercat, Mar 01 2002


Possibly, using a series of heaters (on a single run of piping) that each provides a boost in the temperature of water passing it. Large buildings use an array like that to heat air in ductwork, so I guess some efficiency accounts for using a series of heaters versus a larger central heater and dispersion of air. The same principle should apply to fluids withdrawn from several remote taps. It would seem that the challenge would be to route water so that the hottest water could be withdrawn last from where it would be most useful (? shower) and first from where it would be least useful (? kitchen sink)
-- reensure, Mar 02 2002


I keep reading this as a modern device to produce hooch.
-- neelandan, Mar 02 2002


I did too, every time I see it.
-- StarChaser, Mar 02 2002


You say you like warm, trickling water on demand?
-- reensure, Mar 02 2002


It isn't going to produce that much hot water, because my microwave takes about a minute to heat one cup of water, which would be a pretty dribbly shower! A chap I know living in a trailer recently put in an instantaneous electric heater, the current rating is about 10 times that of my microwave. Even so, it isn't a gusher.
-- pfperry, Sep 07 2002



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