Hot & Cold Lines Crossed?

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Vegas2

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While replacing the hot water heater I turned off the cold water inlet valve and noticed water was still surging in through the hot water outlet pipe. All of the hot water taps in the house were also still fully pressurized, albeit with cold water. After turning off the houses's water main the tank completely drained, only to fill back up when the main was turned back on (with the cold inlet valve still closed). I suspect the builder might have accidentally crossed a hot & cold water pipe somewhere in the house.

Is there any legitimate reason for the hot and cold lines to be crossed like this? The house does have a hot water recirculating system, but there's a 1/2" pipe feeding that pump with a valve that was turned off during the swap, and later completely disconnected during the tank swap.

This also reminded me when we first moved in the downstairs toilet was being feed with hot water (steam billowing up) and the kitchen sink never gets hot water... only luke warm at best. They came out and installed a 1-way valve on the cold water inlet to the hot water tank, which appears to have fixed the toilet heating problem, but the kitchen sink still doesnt heat properly. In retrospect, the cold water throughout the house has always been a bit on the warm side. That plus the hot water tank refilling has me wondering if something else is going on.

Any thoughts? And if they are crossed somewhere, any tips for finding the source of the problem?



P.S. There's no hydronic heating or visible mixing valves. Only extras are a water softener and the RO, fridge, and dishwasher connections under the kitchen sink (all in use).

P.P.S. No luck turning off every faucet / valve in the house including the washer, dishwasher, and toilets. I even disconnected both of the hoses feeding the water heater and cracked the main to confirm the hot / cold stubs weren't reversed. Water started flowing equally from both. The only fixtures still connected during the test were 2 showers (both single handled). The house has flexible tubing in lieu of rigid pipes (neither insulated nor marked) so I could imagine how easy it would be to accidentally cross connect.
 
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hj

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Without doing an additional test, I cannot be sure that your evaluation is correct. A defective single handle faucet could produce the same situation you describe even if the heater were installed correctly.
 

Jadnashua

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If there is a tempering valve, and it was not working properly, you could get flow on the outlet of the WH.
 
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