Hot sea within Cold dampen lines? Temporarily I have scalding hot hose running in my cold hose...

Temporarily I have scalding hot hose running in my cold hose down lines. I have a dual thermostat electric hot sea tank contained by my basement. If I'm not mistaken, this can be cause by either the upper or lower theromstat failing (I estimate this is the problem, as my water cistern did run low on water). The question is, how do I know if it is the upper thermostat, and or radiator coil, or the lower thermostat and or coil?

thanks
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Answers:    You any have a fruitless back flow preventer letting the hot hose go backwards into the cold dampen feed pipe by your hose heater or one of your faucets is unpromising allowing hot water to bleed thru to the cold side.

Your hot marine tank should not nurture into the cold pipes wether ot not you have a doomed to failure heating coil or not.
A discouraging coil is just going to wreak your water to rob longer to get hot or it may not be as hot but it wont motive it to go to your cold sea pipes unless you have one of the problems I first described.
One other route is somebody may have crossed a queue. Have you had any contemporary plumbing work done?