Problem with Hot Water Recirculation Loop

[Dachd]

We recently moved into our house and have an issue with what appears to be a dedicated hot water recirculation loop. When the recirc pump is running, our cold water isn't cold. When the pump was plugged in and running 24x7, you could let the cold water run for 10 minutes and it still wouldn't flow as cold as it should. Even without the pump running 24x7, the cold water still isn't cold and doesn't get cold. This time of year it should be too cold to rinse your mouth after brushing your teeth

Basic info:
>Single-level house on slab foundation, built 2006.
>Location: Northwest Arkansas
>Gas water heater

Picture Notations:

NO IDEA:
The pressure relief valve is routed through the wall to outside. In the pic, where I notated "NO IDEA", you'll see a piece of copper tubing connected to the pressure relief pop-off line at the lower end, and at the upper end, it used to be connected to the tank supply line ball valve with another valve in between.

Recirculation:
>What appears to be a dedicated recirculation loop is connected to the bottom of the tank, between the drain valve and tank.
>Pump has no timer, plug-in for on, unplug for off (currently I have plugged into a smart wifi plug on a schedule)
>Pump & check valve direction: pushing water INTO tank.


Solutions:
The water heater supply line doesn't have a check valve, is adding one the easiest/best possible solution?

If the easiest way to fix this is to add a check valve on the water heater supply side, what's the best type to install?

Can I install something like this: https://www.americanvalve.com/product/g31sl/ in a vertical direction directly onto the top of the tank supply fitting?

It says they need to be installed a minimum of 5 X pipe diameter downstream of any fitting that can cause turbulence...I'm guessing that flex lines cause turbulence. So should I replace the flex line with sweated copper lines?

 

[Terry]

Installing a recirc on a water heater, I install a check valve on the cold supply so that the warm water from the water heater doesn't back up into the cold side.
Sometimes plumbers will install a crossover under a sink and push heated water back into the cold lines, working their way back at some point to the water heater. Not the best option, but I see it done, and have installed them for customers before. It depends on your priorities. Is it important that you are not waiting for hot water? Do you care if the cold side now has heated from the water heater?
The best solution if you can afford it is to have a dedicated return line from the furthest fixture, going back into the water heater. Sometimes piped into the drain with a tee fitting, other times into the cold supply line. Either way, you will want a check valve on the cold supply line.
Rather than running a pump 24/7, I like to wire in an aquastat that shuts down the pump when the return line come back warm.

 

[Sponsor]

 

[Dachd]

Installing a recirc on a water heater, I install a check valve on the cold supply so that the warm water from the water heater doesn't back up into the cold side.
Sometimes plumbers will install a crossover under a sink and push heated water back into the cold lines, working their way back at some point to the water heater. Not the best option, but I see it done, and have installed them for customers before. It depends on your priorities. Is it important that you are not waiting for hot water? Do you care if the cold side now has heated from the water heater?
The best solution if you can afford it is to have a dedicated return line from the furthest fixture, going back into the water heater. Sometimes piped into the drain with a tee fitting, other times into the cold supply line. Either way, you will want a check valve on the cold supply line.
Rather than running a pump 24/7, I like to wire in an aquastat that shuts down the pump when the return line come back warm.

Thanks for the tip on the aquastat!

Re: Check valve, can I install something like this: https://www.americanvalve.com/product/g31sl/ in a vertical direction directly onto the top of the tank supply fitting?

It says they need to be installed a minimum of 5 X pipe diameter downstream of any fitting that can cause turbulence...I'm guessing that flex lines cause turbulence. So should I replace the flex line with sweated copper lines?

 

[Terry]

I'm on the Earthquake Coast, we all use flex connectors.

 

[Reach4]

You should have a thermal expansion tank teed in between the WH cold input and any check valve.