Hi,

I recently purchased a house that has a recirculating pump (Taco 007-F5) with a dedicated line from the farthest fixture (master bathroom tub) back to the HWH where it ties into a mixing valve that is outside the HWH (Honeywell AMX300). When I initially bought the house I was having constant problems where the hot water was backfeeding into the cold water lines where it would come out of the cold side of fixtures. I thought I had a solution when I added a check valve to the cold water inlet, right before the expansion tank. However, I am still getting hot water backfeeding across the flexible supply line that is part of the AMX300 mixing valve and bypassing the check valve (swing check valve btw) and making its way all the way to fixtures on the top floor of the house. I can feel the hot water in the copper pipes as it bypasses the check valve and makes its way (mostly) to the branch line that services the top floor of the house (where all of the bathrooms are).

I haven't been able to determine when or why the backfeeding occurs as it does not happen all of the time but rather randomly as far as I can tell. I have at this point turned off the recirculating pump. Everything operates normally with the pump off but it does take almost 5 minutes for hot water to reach the top floor bathrooms without the circulating pump so the pump would be useful if operating correctly.

Click the following link to see pictures of my setup. At this point, I am thinking that I need to install a more robust backflow preventing device normally seen in more commercial applications in the place of the simple swing check valve I now have installed.

[imgur.com]

Any advice would be greatly appreciated.

Thanks!

2 problems

1)the circulator is the wrong model. you need a brass body circulator not an iron body type.
2)get a circulator with a built in check valve and tie the return from that circulator into a tee at the drain of the water heater. the circulator will have the letters IFC in its model number.
that should solve your issues..

Thanks for the feedback.

Yes, I will replace the pump/cartridge with a SS or bronze model. I have been told the orientation of the pump is also wrong. I will rotate it 90 degrees.

I know that this mixing valve (AMX300) can be used in conjunction with a recirculating pump and return line. In fact, it specifically has a port to connect the return line to (which I have done) as seen in the picture. So, yes, I understand that a typical installation would have the return line tied into the drain of the HWH (and that this would likely solve my issue); however, that is not what I am trying to do. I am hoping to find a solution that allows me to continue using the AMX300 mixing valve as intended. As I understand it, the benefit of having an external mixing valve is that I can keep the water in the HWH at a higher temperature and mix the water outside of the HWH thus also allowing for a greater total volume of hot water.

Would adding an aquastat or other temperature sensor to the return line directly after the pump perhaps fix my issue? This was the recommendation of the mixing valve manufacturer.

Thanks again.



Edited 1 times.

Great Answer!!