I'm looking for a cheap and easy way to extend the amount of hot water available for showers in my house.
I've got a 40 gallon water heater, installed about 1 year ago, and I wish I'd purchased the 50 gallon. In the colder months, it will run out of hot water in about 10 minutes of showering. I have measured the inlet water temperature using a thermocouple pressed against the copper pipe and found that it can range from as low as 8C during the depths of winter to 22C during the warmer months.
I'd like to counter the effect of the super-cold winter water by pre-heating the water before it gets into the tank. I'd prefer a solution that doesn't require any plumbing, but will consider that if I have to. I've heard that there is something called tempering tanks that could be used to store room-temperature water.
I'm considering using a wrap-on copper pipe heating wire or tape on the incoming water line to pre-heat. Something like this or this. I could wire it to only turn on when the burner is activated. I have about 15 feet of exposed copper pipe that I could easily access and put the wrap on.
I'm also considering if I use this method if I should wrap the cold water pipe in an insulating pipe-wrap to avoid losing half the heat to the room. But I worry about overheating the heating wire itself or the pipe wrap.
Would this method work? Is there another method I should consider instead?
EDIT: All of the accessible hot water piping (about 15 feet worth) is already pipe-wrapped. The rest is in the walls, can't get to it.