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We had a hot water re-circulation pump by water heater before and had it removed last December when we detected leaks around it. This is our setup:

We have a return hot water line coming back to the closet where water heater is located. Currently this is capped. We also have a power connection box in this closet for a re-circulator.

I am looking for one that turns on when the temperature on the return line is below a threshold value (say 80 Fahrenheit). I also want this unit to turn on a timer say once in the morning and once in the evening. Plus it should have check valve to allow water from return line to heater ONLY.

Given these requirements, I looked at couple of brands that make circulators. I am confused. They have lot of mumbo jumbo about GPM, pressure ratings kinda details, but don't answer if they have temperature sensitive on/off support included or not. Nor do they specify if the unit comes with check valve.

Can someone who had gone through this exercise before point out any pitfalls when it comes to these sorts of systems?

This is for a rental home and I want to help my tenant.

closed as off-topic by isherwood, ThreePhaseEel, Daniel Griscom, Machavity, mmathis Dec 20 '18 at 14:53

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  • "Questions seeking product or service recommendations are off-topic because they tend to become obsolete quickly. Instead, describe your situation and the specific problem you're trying to solve." – isherwood, ThreePhaseEel, Daniel Griscom, Machavity, mmathis
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  • Rephrased it so that it doesn't look like I am soliciting for product names, instead asking people to what things I should watch out for when settling on a solution. Thanks guys for monitoring and keeping these forums free of fluff and garbage! – PC Guy Dec 20 '18 at 17:02
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This is something that I have had experience with in commercial Energy Management Systems. I can tell you that the first thing you need to look at is the "Payback" or will the cost of this system save enough energy to be worth the installation?

I say this because what you are suggesting can be done but probably not with standard residential grade material. So you are either going to have to buy the control equipment separately or buy a commercial grade product. One requires more manhours and the other requires higher priced equipment and both will need someone with a control skill set to install.

The least expensive control to install would be the time clock either mechanical or digital. I would go with digital where you can program a seven day schedule to come on and off at certain times. They are very common and inexpensive. Almost anyone will do.

Since I am not a plumber, I can't help you with a check valve but that would seem to be a fairly easy install.

The real trick would be the thermocouple which you would have to develope a logic that connects the circulatory pump and the water heater to come on and off at certain times. I would bet that some of the "mumbo jumbo" you read, would recommend that you somehow restrict the flow to get you the proper heat drop (delta T) from the beginning of the line to the end. That may be a better way to go and might be able to be coordinated with the check valve.

In conclusion I would say, you probably won't find a single unit that would do what you are asking for and you would probably need build it yourself. This might include a plumber and a control electrician. So try and get an idea of what you can do for a reasonable cost and work the problem from there.

I usually close with I hope this helps, but maybe I should say to use this answer to start your research and good luck.

  • Thanks @Retired Master Electrician. I am not looking to spend more than $400-500. – PC Guy Dec 20 '18 at 16:59
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This is what I did after I built my house 21 years ago. This is the pump I am using that I installed 15 years ago. ( B&G Model NBF 9U/LW ). You could also use a model NBF- 9U/LW. These are the smallest pumps that I could find at the time. You could also use a Taco or any other brand as long as they are very small and rated for domestic water. This means that they must be Bronze or stainless steel construction. I did not use a temperature sensor, instead, I use a simple plug in timer that you use to turn on some lights when you go on a vacation, and plug the pump into this timer. I turn the pump on/off once every 1/2 hour for 15 minutes (15 on/ 15 off) during the day except for a longer run time in the morning and evening for showers etc. The pump is off from midnight until 6:00 am when the timer again cycles the pump. I have 3 bathrooms and a powder room. I ran 1/2" copper from near each bathroom hot water line and each is equipped with a check valve and a full port ball valve for isolation. The pump line terminates at the old drain valve threaded access point at the bottom of the tank. This has worked for me and it will work for you. Just pick the pump with the lowest pumping capacity you can find and make sure it is bronze or stainless steel including the flanges. My 2 cents.

  • I came across a video on youtube from "This Old House" collection that talked about 3 different ways of doing it. One of the units seemed to address check valve and timer concerns. I might go with something like it instead of solving it with two or three different parts. – PC Guy Dec 20 '18 at 16:56

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