warming the cold water
 

in the winter, the cold water in the house is really cold. to take a shower, you turn the hot on all the way, and add just a little cold. rather than turning up the thermostat on the hot water, which is already plenty hot, any ideas how to warm up the cold water a little bit?

Re: warming the cold water
 

How about a heat exchanger with drain pipes? That's where I can think of some wasted heat to try to take back. Probably wouldn't be possible to make it very effective.

Re: warming the cold water
 

Heat exchangers hooked up to wastewater pipes are against code in many, if not all areas of the US.

Re: warming the cold water
 

If you have a crawlspace under your house which includes your heating duct work, chances are that the crawlspace may be as warm as 55 degrees. If that is warmer than the cold water coming from the supply pipe out of the ground, then perhaps you could install an uninsulated short 30-50 gal storage tank in the crawlspace (like a short style water heater with the insulation removed) so that all of the water travels through it before it enters your house through the floor. Set it up like a water heater so that the water enters the bottom and exits the top of the tank.

Re: warming the cold water
 

You used to be able to get what was called "heat tape" for use on water pipes to keep them from freezing up. You wrap the pipe and then insulate it and plug it in. Meant to just keep the water at around 40 degrees or something like that. Doesn't use much electricity. That is the only thing I can think of.

Re: warming the cold water
 

Heat tape should be available from RV suppliers, as it is used by people who want to use their RVs in cold weather.

Re: warming the cold water
 

+1

Letting your water supply warm up this way will also mean less work for the water heater.

Re: warming the cold water
 

I don't have a crawl space, but my hot water and cold water lines both are located in the attic. you guys are giving me some good ideas, please keep them coming, and thanks.

Re: warming the cold water
 

In the winter your hot water lines, even insulated, will lose heat to your cold attic. Box both lines in together. Waste heat from the hot water lines, which was going to heat your attic anyway, will heat the cold water line instead.

Re: warming the cold water
 

It is amazing how it is against code to recover the waste heat of a shower drain pipe to preheat the cold water pipe going to the shower. That is the easiest way to preheat the shower water. Running the pipe through the attic is the problem since there is not much heat there in the first place and is a great way to have your pipes freeze and burst in the ceilings. Short of that if it is a little warmer up there than the incoming water temp then maybe adding some heat fins to the cold water pipe to absorb some of the heat in the attic would help - will make the water a lot warmer in the summer too.