For those of you who are conducting residential energy assessments; are you recommending "on demand"  hot water re-circ. systems?  I'm finding that many of my customers waste a ton of water while they wait for the hot water to arrive. This is the case even with an insulated pipe because the water is simply wasted down the drain where as a properly configured re-circ system will return the water in the pipes to the water heater.  I recently became aware of a re-circ. system called Switch2o at www.switch2o.com that is enabled when the light switch in the room is thrown. It claims to waste only a cup of water and produces water saving far in excess of dual flush toilets. Thoughts?

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The issue is water is cheap in most parts of the country, a recirculating water system doesn't justify the payback time.

No offense Bob but this is the kind of thinking that has largely been responsible for the depletion of our natural resources.  Wouldn't you agree?

Definitely true.

Agreed. The big issue is natural resource prices have been subsidized by the government for years. Maybe not the water itself, but the electric and gas to heat the water have... At $3 per 1,000 gallons of water payback time on a $500 (installed) recirculation system is VERY long. There is a lot of "lower hanging fruit" in most homes that offers quicker payback times.

Navien has a fantastic condensing 98% efficient unit with a buffer tank AND pump, with internal recirc that can be programmed for when most likely needed AND can be connected to an external recirc loop.  That's the setup I'd recommend.  

I'm going to come to Bob's defense on this.  A recirc is for comfort and convenience.  The water saved is give up multi-fold in energy consumption. 

Is it worth $3-500, and additional BTU loss through a recirc, to save 1000 gallons a year?  

Is your house so good that that $300 couldn't save MORE resources if spent elsewhere?  

Hot water recirc is fairly common here. For some folks, it's a conservation issue because they have wells that don't produce much, so water down the drain is a problem. For others, it's a (usually) energy-wasting convenience that has the effect of conserving water, when what they really want is no wait time.

I'd say the majority of the systems I see are wasteful... over-sized pumps that run continuously, over-sized water heaters pushing water through over-sized, uninsulated lines that are too long. A small percentage are smart... a timer on the pump so that it only operates before/during breakfast and during/after dinner for short periods, an aquastat that turns the pump off if the water in the line is hot enough, short runs of well-insulated piping, etc. 

My brilliant top-secret invention is a faucet that doesn't start flowing water the second you move the handle--it recircs the water until hot water arrives, then it starts flowing. No wasted water, no recirc unless you're about to use water. All you have to do is get used to waiting a few seconds before using the water... which you're probabIy doing anyway. I should be a millionaire soon.

Make it look pretty and I'm sure you will sell some !!

That sounds pretty cool. 

There are plenty of "on-demand" systems out there that are fully integrated already - all you need to do is simply push a button & they stop as soon as hot water is detected - no need to buy a cobbled together "deluxe" system to get that. As for the savings, that depends a lot on the families usage, but most people don't require hot water when they turn on the bathroom light.

As for dependent savings your calculations are based on usage instead of operational costs.  It's all relative.

Switch2o has the cheapest operational cost of the on demand systems and probably similar to the button type. With the button, though you'll need a button at each station.  Also, I know you mean well but this is anything but a cobbled together system.  Perhaps you don't understand the configuration?

Ah ha - you know there is a big difference between "became aware" and I sell or offer... In case of "I now offer" you would have either gotten a private reply, a different worded reply, or none at all.

No it is not relative as it is dependent on a HO's needs, usage & their plumbing configuration. As for the cheapest operational costs - I highly doubt it, unless you have looked into every system out there & run the numbers. I dare say a vacuum switch that doesn't require electricity to start the pump is the most efficient. For the basic- for the thermostat shutoff, maybe but I doubt it - as for the pump, I highly doubt that the pump is the most efficient & cheapest to run unit out there.

A friend of mine set his up using a motion sensor in the bathroom... the pump starts anytime you set a foot inside the room. 

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