For more information on instant hot water, and reducing water waste, see my post on circulating pumps.
The Grundfos Comfort System
You want instant hot water at your fixtures, but you don’t have a dedicated hot water return line? With the Grundfos Comfort System, that is no problem at all. This system by Grundfos is designed for homes without an existing hot water return line. The pump is installed at the water heater, and a special fitting is installed at the furthest fixture away from the water heater. This creates a “loop” in the system, essentially creating a hot water return line.
The pump has two operating modes. First, you can have it running 24/7/365, which will surely save your water usage since you’ll always have hot water at the fixture — no need to run minutes and minutes, or gallons and gallons, of cold water down the drain before your water is hot enough. But my favorite operation mode for this unit is the built-in timer. Setting the timer is simple, similar to setting a lamp timer. You can pick multiple times of day for the pump to run, and for the rest of the time, it is not operating. For example, if you wake up at 6 A.M. and leave for work at 8 A.M., and then return home around 5 P.M. and go to bed at 10 P.M., you can easily set the pump to circulate hot water only for the time when you are home. Not only does this save water by ensuring you have hot water at the fixture while you are home, but it saves energy because the pump is not running while you are at work or asleep.
The Grundfos Comfort PM Auto
The Comfort PM Auto by Grundfos is the “cool new thing” in instant hot water for homes with existing hot water return lines. This pump is very smooth because of its intuitive operation modes. The pump can operate on three different modes: the first, running full time, 24/7/365, which I feel is a waste of energy. The second, which is only slightly better than running the pump full time, is setting the pump to kick on when it detects that the water in the hot return line is no longer the same temperature as the water exiting the water heater. This is better than having the pump run full time, because it reduces the amount of time the pump is running; however, the temperature in the hot return line may trigger the pump to turn on several times over the course of a day, while nobody is home or using hot water. The third feature, which is my favorite thing about this pump, is that you can set it to “auto”. The pump has a built-in computer, a “brain” if you will, that after roughly one week of use, “learns” your routine and adapts to your water use. The pump knows when you wake up — and when you go to bed — and when you’re at work, and only runs during those times when it knows you will want hot water.
The Metlund D’mand Kontrol System
This system is the ultimate solution to both water and energy conservation. This slick system installs underneath the fixture furthest away from the water heater. (Please note: you will require an electrical outlet at this point, and if you do not have one underneath the sink, or do not want to have an electrician install an outlet, this system is not for you.)
This pump is so great because it is a truly on-demand system. Unlike the other two pumps I mentioned above, this pump is manually operated. It features a button that you can mount on the face of the cabinet (or somewhere less conspicuous, like inside the cabinet door). When you are ready to use the fixture (generally a bathroom sink), or perhaps a shower only a few feet away, you simply push the button and the pump kicks on. It pulls hot water from the water heater to the point of use then shuts off. You now have hot water already in the line, ready to use. This system is ideal for homes where one bathroom or fixture in particular is especially far from the water heater.