Tankless water heater vs. comfort pumps

Does anyone know the pros and cons of a comfort pump for immediate hot water? I've been checking out the tankless types and the cost is reasonable for the unit, but almost prohibitive for installation. Then I saw a flyer on these comfort pumps, where you install just below any sink a valve..no electricity required and the main pump on top of your existing water tank. With the tankless ones, one has to update a 100 amp main ( in my case ) to 200 amp and that does not include the plumbing installation.
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Look here for a description of the Grundfos one-I saw it a while back in JLC magazine:
http://www.rewci.com/whhohotwaci.html
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The particular product you point us to claims the following: "Save Up To 16,000 Gallons Of Water Per Year, Per Household (Based on average modern household usage) And Uses Less Energy Than A 25-Watt Light Bulb! A Breakthough In Home comfort!"
It's a recirculating pump.
Less energy than a 25W bulb? Under ideal conditions, for the pump only, maybe. The reason the water at the tap is cold in the first place is that it can't stay hot in the pipes. Water in the pipes approaches the temperature of the inside of your walls by losing or gaining heat through the walls of the pipe. Hot water, obviously, loses heat into your walls.
The pump puts this now cooler water back into the water heater, where it can be heated up again. That takes a lot more energy than a 25W bulb!
Let's assume that it's always Winter when you're using this recirculating pump, so you're running your furnace to heat your house. Let's also assume that it costs no more per BTU for you to heat water than it does to heat the living space in your house. Finally, let's assume all the lost heat from your hot water piping escapes into the living space of your house.
In that case, the energy required to re-heat that cooler water is a wash--you're just going to run your furnace less and your water heater more.
Otherwise, just let the hot water run for a minute or two before you jump in the shower.
The other selling point--16,000 gallons/year? If you have 5 people showering (2.5gpm) every day, AND it takes 3 minutes for the water to warm up AND they each start their shower with completely cold water in the pipes, AND you waste some more water waiting for the sink to get warm for dishes or shaving...
16,000 gallons/year is a bit of a reach.
If your family is wasting that much water, there's probably a lot of things you can do to use less of it. Things that don't involve spending any money at all.
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the pump idea has been around for 15 years or more that I know of. I had a "package unit" that was installed in my fartherest bathroom. I had it on a on delay timer. The pump would run for 2.5 minutes and there was hot water available. Problem is the SO never remembered to push the button when she went into the bathroom. I do mean never.
There is also an idea for the toilet that uses hot water for the first flush or when the thermostat does not sense hot water.
I resisted the idea of a timer or t-stat so the pump was constantly running. My package unit had a timer but the shortest period I could set it to was 30 minutes. I disabled the timer the first day.
Do your home work, and like the other poster said. Saving are bunk. It is all about convience. The amount of water wasted makes so little difference in you bill. The cost of heating it is much greater compared with the cost of the water.
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go to al's, great info for you on a rinnai gas water heater: http://www.alsheating.com/RinnaiWaterHeater.htm
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