Hot water recirculation with return line. Working examples?

[tony14]

I want to install hot water recirculation with return line to our kitchen sink. It's about a 45-50 foot run from the water heater, 3/4" copper pipe. I'm finding it hard to find simple, straightforward examples of this online.

I would be grateful for information and/or examples that will help me determine the following:

1) Diameter of pipe. 3/4"? 1/2"?

2) Maximum rate of flow. I understand too much velocity can shorten the life of copper piping.

3) Copper? PEX? PEX being easier to run.

4) If PEX, any particular kind so it can handle the constant heat?

5) Whether it's better to let it run continuously (say 16 hours a day) or intermittently to keep the hot water in an acceptable range? Does intermittent operation wear the pump out sooner?

6) Pump brand/models that are a good match based on what is decided above.

 

[Twowaxhack]

Here’s the pump I use. It’s good like bacon. You’ll also need to buy the flange kit.
https://www.zoro.com/armstrong-pump...VVBOtBh1TvQFjEAQYCCABEgKXxPD_BwE&gclsrc=aw.ds
Install check valve on cold water supply to water heater , then install an expansion tank, then install a tee to connect the 1/2” (3/4” would also work at a lower velocity) return pipe from your kitchen sink. Before you connect the return line to the tee, install the circulator inline. Directly before the circulator install a ball valve. Then the circulator pump, then a a boiler drain then another ballvalve. Then connect to the tee I mentioned at the top of the water heater on the incoming cold line.

Insulate all the pipe you can. Use pex A or copper. Pex a can be expanded, crimped or cinch clamped.

Read the instructions on installing the pump and follow them.

The boiler drain will help you get the air out. The ball valves will help you isolate the pump for maintenance and replacement and general troubleshooting.

Leave 12” of pipe between connections if you can. Gives you room to work on the system if needed without disturbing other joints.

Run the circulator on the slowest speed possible that suits your needs. Most likely that’ll be on the low setttng.

 

[MicEd69]

Well here's one simple diagram for your system.



1) Diameter of pipe. 3/4"? 1/2"? 1/2" is fine for the above sketch.

2) Maximum rate of flow. I understand too much velocity can shorten the life of copper piping. 5 GPM

3) Copper? PEX? PEX being easier to run. Copper

4) If PEX, any particular kind so it can handle the constant heat? N/A

5) Whether it's better to let it run continuously (say 16 hours a day) or intermittently to keep the hot water in an acceptable range? Intermittent on Demand
Does intermittent operation wear the pump out sooner? No

6) Pump brand/models that are a good match based on what is decided above. Grundfos, Goulds, others

Mine only runs when I switch it on manually when anticipate I will be using hot water. That reduces energy used in pumping and reduces heat loss through my insulated piping.

After reading Twowaxhack's response, I do need to mention that this sketch doesn't show an expansion tank. You do need one by code in some locations, and you definitely need one if you have a check valve in the supply line to the water heater, or a pressure reducing vave in the water supply if it hasd an integral check valve.

 

[breplum]

Add a timer and aquastat to your system, better yet, add remote trigger. Easy system integration: Home or look up D'mand

 

[Mitchell-DIY-Guy]

If you have any kind of “head” to your system (such as water heater in a basement) you may not need a pump at all. Just search for thermosiphon hot water circulation.

 

[tony14]

Thank you all kindly.

 

[William R]

Tony
I would encourage you to look at a different solution to provide instant hot water.
Your current path is a lot of work, expensive and will result in a lot of energy waiste
Check: Smart Recirculation Control - Hot Water Pump Controllers
They have simple solutions that will only trigger the hot water recirculation on demand with products that are easier to install.
The genius of the system is the trigger. If you want hot water simply turn on and off the hot water line for a couple of seconds from the sink or area of the house you want hot water. That will start the pump and depending on the distance from the hot water source you will have hot water available very quickly.

 

[tony14]

Thanks, I'll check it out. We are comparing all the various options.

 

[Mitchell-DIY-Guy]

The genius of the system is the trigger. If you want hot water simply turn on and off the hot water line for a couple of seconds from the sink or area of the house you want hot water. That will start the pump and depending on the distance from the hot water source you will have hot water available very quickly.

That is a great idea. The problem with all these timer schemes such as those pre-packaged from Watts and others, is that you need to have very predictable usage of hot water. For example, you get up EVERY morning at 6:00AM and are in the shower at 6:15. That works for some and not for others. It would have never worked for me, ever. I had a passive recirculating hot water return and I cannot say my gas bill went up very much. My electric bill didn't go down when switching all to CFL and then LED either...though it was supposed to.

 

[havasu]

A cheaper way to activate a recirc system is to install either an app activated 120v plug, or an even cheaper way would be to plug your recirc system into a remote on/off Christmas light plug receiver. They run ~$15.

 

[William R]

That is a great idea. The problem with all these timer schemes such as those pre-packaged from Watts and others, is that you need to have very predictable usage of hot water. For example, you get up EVERY morning at 6:00AM and are in the shower at 6:15. That works for some and not for others. It would have never worked for me, ever. I had a passive recirculating hot water return and I cannot say my gas bill went up very much. My electric bill didn't go down when switching all to CFL and then LED either...though it was supposed to.

Not a timer scheme. I had one of those and you are correct, they just don't work when you need them and work too much when you don't. This is a system you activate by turning the hot water on for a second or two to wake up the pump. If you are not concerned with the waisted water that flows before you get the hot water - this is not for you.
For me, I find it very convient to activate the hot water pump at the sink before taking a shower. When I start the shower - I have instant hat water.

 

[Twowaxhack]

I have a customer that his circulator set up with Alexa. He walks in the bathroom and says “ Alexa hot water “ and the pump starts for a set time.

He doesn’t turn on the faucet until about 30 seconds later and the water is hot within 2 seconds. It takes 2 seconds to purge the faucet and pipe from the loop.


Another customer uses a motion detectors in each bathroom. Walk in the bathroom and the pump starts for a set time.

And some have push buttons to start the pump for a set time.

I have another guy that runs his circulator 24/7.

 

[MicEd69]

A pushbutton in the kitchen and one in the master bath, runs for 2 minutes, instant hot water to all locations.

While I am and engineer, kiss is more than a motto. Timers are a sure thing when compared to a temperature sensing device.

 

[William R]

A cheaper way to activate a recirc system is to install either an app activated 120v plug, or an even cheaper way would be to plug your recirc system into a remote on/off Christmas light plug receiver. They run ~$15.

Looked into those and rejected all of them.

The app thing sounds cool, but I really don't want to find my phone, open the app, and then turn on the pump. The other issue is now I need to remember to open the app and tun it off when I am done using hot water. Too much work, too many issues.
The Christmas light plug thing is awesome for Christmas lights - just set mine up for the Christmas tree. Love it. The problems in using that for hot water pump control include:
- I would want a remote at every hot water source - for me, that would be 7 remotes
- Could all the remotes be programmed to the same plug?
- Would many of the remotes would be out of range?
- Would they get lost or wet
- I would have to remember to also turn them off after each hot water use
With the Smart system I just turn the lever on and off for a second or two. Pump is activated. Only takes 1-2 seconds. NO looking for a switch or phone. No apps to open and use. And the big bonus is it will automatically stop the pump after 5 minutes or so.

For those folks that do not have a hot water recirculating system and don't mind waiting a wasting cold water - they should just keep doing what they are doing

For those that already own or want to install a hot water recirculating system and want to conserve both water and energy and money - the Smart controller is (in my opinion) the absolute best answer.

For those that just want the convenience of Hot water on demand and really don't care about the energy or money wasted - they should run that pump 24-7

All choices are personal


Just want to share the option I found.

 

[William R]

I have a customer that his circulator set up with Alexa. He walks in the bathroom and says “ Alexa hot water “ and the pump starts for a set time.

He doesn’t turn on the faucet until about 30 seconds later and the water is hot within 2 seconds. It takes 2 seconds to purge the faucet and pipe from the loop.


Another customer uses a motion detectors in each bathroom. Walk in the bathroom and the pump starts for a set time.

And some have push buttons to start the pump for a set time.

I have another guy that runs his circulator 24/7.

I like the Alexa option if you don't mind having an Alexa devise listing to you near every hot water faucet. The big issue is you need to remmber to have her turn it off

 

[Twowaxhack]

I like the Alexa option if you don't mind having an Alexa devise listing to you near every hot water faucet. The big issue is you need to remmber to have her turn it off

Nope, it only runs for a few minutes then the pump turns off. By then you have hot water to the bath.

He has Alexa all over the house

 

[havasu]

At my house, one faucet is 100 feet from the water heater. I would have to activate the water, walk away for 3-4 minutes to walk into a hot shower. Now that I'm retired, my schedule is pretty consistent. Wake up at 630, shower at 9, lunch at 1, dinner at 6, brush teeth and wash face at 11pm. 5 tabs flipped on my Grundfos timer is set so the faucets are hot during those times. I guess if one is predictable, why build a more costly mousetrap?

 

[Mitchell-DIY-Guy]

really don't care about the energy or money wasted

In Michigan where I lived, we used heat from about September 15 until May 15. For certain, there were times in the first month of that season, and the last month of that season as well, when you did not necessarily need heat, but for certain the heat was being used periodically. So that's about an 8 month heating season. Whatever heat loss I had from the passive thermosiphon recirculating hot water was heat that stayed inside the building envelope, so in a sense that's not wasted. Just repurposed!

In SoCal, of course, your life is different. Ditto for @Twowaxhack in the gulf area. In the summertime here in NC, my "cold" water comes out of the faucet at about 82 degrees...

 

[tony14]

As the original poster, I have found this all very interesting. It does confirm our preference, though, which is a combination of timer and temperature sensor. The timer would shut the pump down during sleep hours, and the temperature sensor would keep the hot water ready at the kitchen sink the rest of the time without running the pump constantly. The recirculation is only for the kitchen sink--the rest of the faucets are close to the tank except tor the clothes washer in the garage, and we plan to get a new washer that will heat the water as necessary so no need to heat the long run to the garage.

I would like to use a Grundfos pump, a low-flow (~2.2 gpm) model that provides temperature sensing. I believe the model that does that is the UP 10-16 Temp BU LC aka 99412493. For the timer capability I would use the same small plug-in timer model that we currently use for, guess what, the Christmas lights.

The problem I'm running into is the Grundfos documentation. The installation instructions appear to cover several models in the UP 10-16 class, and it's not clear to me which model is being addressed in each of the sections. After reading it, I'm not at all sure how the temperature mode--and therefore, presumably, the 99412493--works. Does it come with a cabled sensor that would go on the hot pipe somewhere? I would think so but don't see it clearly stated anywhere.

If anyone has experience setting up one of these pumps in temperature mode and can advise me, I would be grateful.