Best heat source for water?

[5Runner]

I am planning to build a hot water circulation system into my vehicle. It will consist of a 5 gallon tank, a recirc pump, valves, a sink sprayer and a heat exchanger. The concept is the pump will circulate the water as it heats it up and will shut off after a set temp is reached. The loop will then be closed with a valve and the dry run pump turned on to generate pressure for use. I have already read this thread. http://www.expeditionportal.com/forum/showthread.php?t=34048


Here is a long and skinny tank that will fit right in front of the gas tank of a third gen 4runner with a 1.5 inch body lift.

http://www.plastic-mart.com/class.php?item=240



The question is this...


What do you think is the best heat source for me to use for the water.

--- THE EXHAUST PIPE---
Pros:
-- It is right next to where the tank will be and the sprayer which will be at the back of the vehicle. Also the pump will be behind the back seats.

-- It will be easy to wrap the copper tube around to build the heat exchanger.
http://www.bio-power.co.uk/exchanger.htm

-- It "might" heat up faster than the radiator alternative

Cons:
-- I can't find anyone that has done this already to get feedback on

-- Will it get too hot? Not hot enough? Who knows?




--- THE RADIATOR PIPE ---
Pros:
-- It has been done before.
http://www.hotcampshowers.com/

-- I know it works

Cons:
-- Not in a good spot. I will have to run pipe way out of the way up to the engine area.

-- Takes a long time to heat up.



Does anyone have any suggestions, ideas, thoughts or what ever?

Are there any other heat sources I am not thinking of that could work?

Thanks!

 

[chasespeed]

There are other options, though, complication might be an issue.

I DO like the idea of diverting coolant, and using that. There are a couple ways to do that, w/o taking up a LOT of space. One thing I would look at, is a good quality stacked plate heat exchanger. That keeps the fluids seperate, and you can have a thermostatically controlled pump controling the flow of potable water through the heat exchanger.

You could also use something similar with engine oil(might be a better option for us diesel guys, which, in some cases, can take a LONG time to get up to temp w/o a load). Same concept.

Either of these would allow the system to be a little more compact. Pump would be mounted just outside the tank, and there would be 2 hoses running up to the engine bay(you could even sleeve them in a foam insulation to protect against abrasion, and retain heat). The heat exchanger would stay in the engine bay.

Insulate your water tank, and you could be pretty good off.

The exhaust thing, I am a little weary of. But that is just me. Soft drawn copper will eventually work harden I THINK , in a situation like that. A lot of heat cycles, vibration, and under heavy load, a LOT of heat. But, thats just my opinion.

A well, planned out system , can be simple(as possible anyway), reliable, and easy to repair if needed.

Chase