I currently have a 50 gallon hot water tank that is heated by natural gas. I've been thinking of changing over to an on-demand hot water system. Here's the problem. I live in Montana. It's winter. And I just measured the temperature of the incoming water from the main at 39°. Is there an easy way to Simply preheat water using Ambient Air Temperature in the basement before it goes into the hot water on demand unit? I've read other posts that say you need to run it into a non-insulated large container that the water would be used to feed the on-demand tankless system. Are there any on demand systems that would easily bring that incoming 39° water to 110° or would the flow be reduced until the hot water is hot enough to be discharged. Or would the water just flow through the unit and come out warm instead of hot. I'm not sure of the internal mechanism of the on-demand systems. Thanks in advance for your input

I have a 50 gallon hot water tank that is heated by natural gas. I've been thinking of changing over to an on-demand hot water system. Here's the problem. I live in Montana. It's winter. And I just measured the temperature of the incoming water from the main at 39°. Is there an easy way to simply preheat water using ambient air temperature in the basement before it goes into the hot water on demand unit? 

I've read other posts that say you need to run it into a non-insulated large container that the water would be used to feed the on-demand tankless system. Are there any on demand systems that would easily bring that incoming 39° water to 110° or would the flow be reduced until the hot water is hot enough to be discharged. Or would the water just flow through the unit and come out warm instead of hot. I'm not sure of the internal mechanism of the on-demand systems.

Thanks in advance for your input