Dual Recirculating pumps - return lines swapped

[farmerfloyd]

We have two hot water heaters with independent circuits. Both have return lines that connect to a recirculating pump. We realized that the return lines are crossed and return to the opposite water heater. This has caused cross talk with hot water coming from our cold water line. Not sure why, but when I shut down the two recirculating pumps, this stops.

I want to correct the issue, but the metal corrugated lines that connect the pump back to the water heater are too short to connect to the opposite water heater. I'll need a 1/2" FIP x 1/2" MIP x 30" line, but want to make sure I choose one that is up to code. I can make due with an FIP x FIP hose and use an adapter, but that's just the type of line it is currently.

In the picture, you'll see that I have to connect the left pump (red) to the right water heater and vice versa.

Thanks!

 

[breplum]

Ultimately you will want to get the piping going right. I suggest a plumbing contractor for that.
To do your funky temporary fix you can use two water heater flex and a brass nipple to connect them. We don't use that crappy copper flex anymore. Stainless steel rules.
That equipment is so old that you are going to be replacing sooner rather than later.
When you see the price to replace two WH, consider one Tankless WH with an internal pump, Noritz or Navien (I recommend Navien). Then add a pair of circuit setters and feed the circuits from a single 97% efficient source.

 

[farmerfloyd]

Thanks for your reply!

Is there anything particularly bad about using the temporary fix other than it will look weird? The house is nearly 20 years old and when it comes to replace the water heaters, I'll do the full correction of the piping. We are probably going to repipe the house in the future as well.

Will the system you recommended above be adequate to produce enough water pressure and volume of hot water for a family of 5, with 4 full baths? We frequently shower when we use the dishwasher/clothes washer.

Thanks for any input - much appreciated

 

[breplum]

It is possible a fouled check valve with some rust trapped, or a bad mixing shower valves, like Kohler 304 that needs parts replaced.

No I don't believe there is anything wrong with your idea if you are absolutely sure the original plumbers were that stupid.

 

[farmerfloyd]

The hot water in the cold water line is most noticed in the laundry room which is on the opposite side of the water heater. When I shut down the recirculating lines - it didn't happen at all. If it still happens after I correct the plumbing, then I'll look at the check valves.

They indeed were that stupid. I found out when we had a slab leak of one circuit and shut down that water heater. The other water heater then did not have recirculated hot water. After the fix, I only turned on one pump and the faucets that were heated was from the other water heater. They also used gal for the main lines with pex coming off of it - ended up with a leak at a corroded elbow of the main line and flooded a room in our house.

Thanks so much - I really appreciate your expertise.