I added a hot water recirculating pump to an existing dedicated hot water return line. Does the setup look acceptable?

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Plumbum1234

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I added 5 feet of 1/2 in. Type L copper pipe. I connected it to the existing hot water return line which has gate and check valves.

The second picture shows the connection of the new pipe to existing gate valve with a SharkBite elbow. That run is 6 inches.

The third picture shows the hot water recirculating pump connected to the newly added 4.5 ft. of vertical pipe and tank drain. The pump is AquaMotion Stainless Steel with Check Valve, Model AMH3K-7.

My questions are:
  • Does this setup look acceptable or a very obvious DIY job?
  • Should I support the 4.5-foot vertical run somehow? Or should I extend it to the floor and use a drop-ear elbow, for example?
  • The pump hardly moves when on, but should I secure it to the concrete floor? If so, is one location better than the other?
  • Lastly, should/can I insulate all the copper pipe, or should I leave some exposed so it cools down quicker. I read somewhere online to leave the last 15 feet uninsulated.

Thanks in advance!

PXL_20220209_165139995.jpgPXL_20220209_165147650.jpgPXL_20220209_165155079.jpg
 
Wow. Never heard of it done that way before.
 
Plumbum1234 said:
Yea, I read that was acceptable. If you go here and click on the instruction sheet, you will see that it can be attached to the drain. AquaMotionHVAC.com » AMH2K-7. It's a different model but same concept. I also asked the OEM and they said it was okay.
Click to expand...
I just looked at the sheets on this model and I am not seeing it hooked up that way.
 
All hot water piping inclucing all the recirc pipe should be insulated with minimum 3/4" thick insulation.
No plumber would say it is a good job.
 
I'm just going to answer 2 of your questions, and comment on the connection back to the water heater.

Q - Does this setup look acceptable or a very obvious DIY job?
A - It absolutely looks like a DIY job!

Q - ...should I extend it to the floor and use a drop-ear elbow, for example?
A - No, because that would make the answer to the above question, "It ABSOLUTELY looks like a DIY job!!!!!"

Connecting the return line to the bottom of the tank is entirely acceptable. However, the drain hose bibb should be removed and brass fittings added so that a drain valve remains for the tank. It makes no difference to the water heater whether the returning warm water goes down the dip pipe on the cold-water inlet to the bottom of the tank, or directly into the bottom of the tank through the drain valve connection.

A more professional layout would be to install a "shelf" on the wall to get the pump off the floor. Run a line vertical up from the new brass fitting out of the water heater drain connection so the piping to the pump is not in front of the gas burner access; maybe 3 feet or so for easy access. Run the connection to the existing return line over to the wall at the ceiling of the basement so it does not come down in front of the water heater. And rather than using the flex hoses, hard pipe the pump and that would result in a less DIY looking installation.

Oh, and as breplum said, insulate the piping.
 
With the return piped to the bottom there has been reports of problems for some systems, depending on the temp drop of the return water.

This can cause the burner to fire too often and the lag between on and off can over heat the tank. It’s basically stacking caused by the return water being well below the set point of the thermostat

So the manufacturers started recommending a top fed return that uses the dip tube. Manufacturers started making the dip tubes shorter to prevent stacking by the user, this was done years ago.
 
Twowaxhack said:
With the return piped to the bottom there has been reports of problems for some systems, depending on the temp drop of the return water.

This can cause the burner to fire too often and the lag between on and off can over heat the tank. It’s basically stacking caused by the return water being well below the set point of the thermostat

So the manufacturers started recommending a top fed return that uses the dip tube. Manufacturers started making the dip tubes shorter to prevent stacking by the user, this was done years ago.
Click to expand...
I did not know that. Makes sense. Thanks for the clarification.
 
MicEd69 said:
I'm just going to answer 2 of your questions, and comment on the connection back to the water heater.

Q - Does this setup look acceptable or a very obvious DIY job?
A - It absolutely looks like a DIY job!

Q - ...should I extend it to the floor and use a drop-ear elbow, for example?
A - No, because that would make the answer to the above question, "It ABSOLUTELY looks like a DIY job!!!!!"
Click to expand...
LOL! Words that make any self-respecting conscientious DIYer cringe: "it looks like a DIY job" .
 
SHEPLMBR said:
These are for well tanks. Do it the correct way like I posted. You wanted honest opinions, that's what I am giving you. Expect nothing less. I would fire anyone who did it this way.
Click to expand...

That's exactly why I posted on here. I knew something was "off." And by no means was I trying to argue with you, and I am sorry if I gave that impression, I was just posting what the OEM said. I also have a quote from a local, licensed plumber who also was going to tie it into the tank drain. With that being said, if best practice is to tie it into the cold-water supply, then I will install it that way.

Here's my plan:
  1. Demo some of the existing dedicated hot water return line (in white in the picture)
  2. Attach the recirculating pump to the first-floor joist with a vibration pad (in blue in the attached picture/highlighted yellow in my drawing)
  3. Add 1/2" isolation ball valves before the inlet and after the outlet (the two elbows before the inlet and after the outlet will be at least 3" away to help prevent flow disruption) (in blue in the attached picture/highlighted yellow in my drawing)
  4. Tee into the existing 3/4" cold water supply line prior to the water tank inlet (in blue in the attached picture/highlighted yellow in my drawing)
  5. Insulate
  6. InkedPXL_20220218_122505887_LI.jpgasas.jpg
 
MicEd69 said:
I'm just going to answer 2 of your questions, and comment on the connection back to the water heater.

Q - Does this setup look acceptable or a very obvious DIY job?
A - It absolutely looks like a DIY job!

Q - ...should I extend it to the floor and use a drop-ear elbow, for example?
A - No, because that would make the answer to the above question, "It ABSOLUTELY looks like a DIY job!!!!!"

Connecting the return line to the bottom of the tank is entirely acceptable. However, the drain hose bibb should be removed and brass fittings added so that a drain valve remains for the tank. It makes no difference to the water heater whether the returning warm water goes down the dip pipe on the cold-water inlet to the bottom of the tank, or directly into the bottom of the tank through the drain valve connection.

A more professional layout would be to install a "shelf" on the wall to get the pump off the floor. Run a line vertical up from the new brass fitting out of the water heater drain connection so the piping to the pump is not in front of the gas burner access; maybe 3 feet or so for easy access. Run the connection to the existing return line over to the wall at the ceiling of the basement so it does not come down in front of the water heater. And rather than using the flex hoses, hard pipe the pump and that would result in a less DIY looking installation.

Oh, and as breplum said, insulate the piping.
Click to expand...

I appreciate your input. I took your advice and blended it with input from others (thank you all as well), what are your thoughts now (I believe my response will be right above this comment)?
 
That hand drawn pipe diagram is improper. Your hose Bibb will be getting return water.

no check valve and you will need an expansion tank.
 
Last edited:
You are getting close but tying into your cold-water line there is still wrong. You need to tie the warm water return to the cold-water inlet of the water heater below the valve on the water heater. You should also install a check valve in the cold-water inlet to the water heater above that tie-in point so you don't pump warm water backwards into the cold-water line.

I didn't look up the pump, but SHEPLMBR said these pumps are for well tanks. And as most hot water circulating pumps are line mounted and do not need to be mounted on a joist with a vibration pad, I'm thinking this isn't the correct pump.
 
Twowaxhack said:
That hand drawn pipe diagram is improper. Your hose Bibb will be getting return water.

no check valve and you will need an expansion tank.
Click to expand...

Good call. For what it's worth, there is a check valve built into the pump. I understand why you would want a check valve upstream of the tee (and therefore an expansion tank is needed), but won't the hose bibb be primarily supplied by the 3/4" supply line opposed to the 1/2" return line?
new.jpg
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