There is. This is the only one that I found when searching a pre-existing solution:
There was a big flaw with the design of this solution. I didn't like the idea that it would circulate the hot water back into the cold water pipe. I want my cold water to be cold and my hot water to be hot! I also didn't like the cost for what was a low power basic pump.
Without knowing what my pump solution would be I set out to run return lines from the two ends of the house back to the water heater. I tapped the hot water pex line underneath the bathroom sink (in the ceiling basement) and also the hot water line right below the kitchen sink. I ran these lines through the basement back to the utility room with the hot water heater.
Here's a rough drawing not to scale:
This is the pump I bought:
The check valves were added before the two return lines were combined. This keeps the hot water from circulating backwards (the long way) through the line. The flanges have a 3/4" female thread.
To connect the pex system to the flanges I bought these in store at Home Depot:
- 1/2 in. Brass Push-to-Connect x 3/4 in. Male Pipe Thread Adapter
- 3/4 in. Brass Push-to-Connect x Male Pipe Thread Adapter
The return line I used was 1/2" pex and the output line was 3/4" pex to match the cold water intake of the water heater. Here's how it's all hooked up:
You'll have to roll your own power solution. I hooked up the pump to an insteon automated light switch. With this solution I can turn on the pump at different times of the day. You could use a simple timer connected to a standard plug if you wish.
Here is the final picture. I added insulation to as much of the hot water piping as I could. I mounted the pump to a block of wood which I screwed into the joists.