Someone I knew once suggested an idea a few years ago that I’m going to post here for your comments. I’ve thought about the idea a bunch since then and I’m not convinced it will work but who knows, maybe one of your comments will stir something up…
As you know, your water supply comes into your house via a pipe carrying cold water. From there it’s distributed to your hot water heater and your boiler for your heat (assuming you have a gas heat system).
In the winter the water coming into your house is insanely cold and your boiler and hot water heater have to do a lot of work to get it to a useful temperature. My friends idea was to add a tank or bladder into the mix and put it between the cold water source coming in from outside and the heating systems. This way the cold water presumably would have a chance to come up to room temperature (or at least rise a bit in temperature) before it goes to be heated with the gas. This could make a big difference in the winter when it’s 60+ in your house and it’s 0 outside. Instead of a bladder you could convert right away to a flexible hose and just have a few hundred feet or so of it up in your ceiling.
To me, this seems like a good idea but I wonder a few things. First, how much temperature gain would you get? It would depend on how much time the water is sitting there not being used and also how well heat transfers into the tank/bladder/hose. Secondly, is it possible for the huge amount of near freezing cold water to actually lower the ambient temperature in your basement (where the tank/hose would be)? Thus making the heating system need to do more work?
Hard to tell w/o experiments.. What do you guys think?