Device Could Help Save Water While Hot Tap is Warming Up

Waaaaaaaaaay too complicated. This has already been done years ago. Here is Taco Pumps version of a device to circulate the "not yet warm" water back into the cold side.

http://www.taco-hvac.com/en/products/Hot-Link%26reg%3B%20Domestic%20Hot%20Water%20Recirculation%20System/products.html?current_category=398

Others have done similar things with circulators that are wired into the "remote" sink.

Once the hot water hits the thermo-valve, the valve cuts off the re-circulation. There is a timer so it's not trying to circulate water when the household is either unoccupied or sleeping. I like this concept because you can have one circulator pump and multiple thermo-valves if you have multiple branch circuits on long runs.

Cheers !

I have to agree with Mr Robin, Way to complicated, Way to expensive.

On top of it it will not work, for a simple reason of water pressure balance.

Much simpler solutions exist: start with brushing your teeth and use the first colder water.

If it is still to long cold afterwards: invest in a flow hot water generator under the tap. Will cost you much less in the long haul as all that cooled water in your tubes did cost money to heat it first.

A simple system based on trace heating can also help and this system can be programmed to heat the water above 70°C once a weak, to bacteriological clean the inside of your tubes. Check HWAT

Trace heating is a clever idea as well.

I suppose one would need to look at the cost to provide bulk heating of the water (natural gas in my case) along with the cost of the volume of water "wasted waiting for hot" against the cost to maintain a given volume of water at temp (of course only during usage times using timers) using electricity. And then amortize the costs of the trace heaters over a number of years. Would be interesting to see how the numbers fall out. Fortunately for me, our water costs are pretty reasonable. We're paying about $90 per month for four teenagers and the missus and me for our municipal water and sewer. We don't have a pool and I don't make a habit of outdoor watering unless I have to. I'm sure others in more water sparse areas probably pay a much higher rate.

Anybody in California want to chime in on their water charges?

All these systems only make sense in a bigger scale: domestic hot water distribution is not the area where these systems are to be used.

With trace heating and circulation systems you can keep the main water bulk above 55°C, which is important for hygienic reasons.

Bigger systems also have bigger pipes (domestic is mostly limited to DN20 (3/4")) flushing these in the morning when you need to start washing the first patient is not practical.

For domestic I must admit that the best system is the local hot water generation (electricity or gas), local is directly near the tap without storage. These systems, if maintained and installed correctly, have the best efficiency.

All other approaches should start with decent insulation of all hot water lines. Trace heating has one advantage over circulation: you only have one pipe to install and keep warm. It is also easire to regulate over the day, keeping the total energy consumption reasonable.