# Producing hot running water



## Michael Kawalek (Jun 21, 2007)

I thinking about different schemes for producing my own hot running water. Our cabin is in a sunny southern exposure, so I want to try a solar batch collector first. I'll try the recycled water heater tank idea. I realize though that this will only produce hot water in the summer months and needs draining come winter. 

I just bought an old Monarch wood cookstove and am thinking about producing hot water with it. It has a hot water reservoir on the right side, and am wondering about adapting it to making hot RUNNING water. What I envision is running a coil of copper tubing inside the reservoir to absorb heat from the hot water. 

My first question is how hot does the reservoir water actually get? Can I expect 120F or 210F water. How long does it take to get hot? If hot, how many feet of copper tubing will I need to absorb the heat? 

A second idea is instead to wrap copper tubing around the stovepipe exhausting the stove. I'm worried though that this might be potentially dangerous if the water boils inside the tubing. It could cause an explosion. Is this a realistic concern or is it not something to worry about? Again, how many feet of tubing do you need to absorb enough heat for a hot shower? I have not plumbed the cabin for running water yet so I am free to run pipes wherever I chose. 
Michael


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## Ross (May 9, 2002)

The smoke pipe heat exchangers I've seen are just short U tubes inside the smoke pipe. Don't discount winter solar collection I have a south facing roof that drips water on the coldest days and that was before it was even heated inside!


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## WisJim (Jan 14, 2004)

Years ago I made a copper tubing heating coil to go around the stovepipe. It worked well, but we moved and our stoves are arranged differently now, and we have a forced air wood furnace with a water heating loop in the firebox. Our current system with the water heating loop in the firebox which circulates to a 60 gallon tank which feeds a 40 gallon water heater, is usually 110 to 125 degrees in the 60 gallon tank, when there is a fire going all the time in the furnace. Our old system didn't have a way to monitor water temps, but it never got near boiling.

The copper coil went around the outside of the stovepipe, to make cleaning the pipe easier. It worked by gravity circulation of the hot water, with no valves or restrictions between the tank and the coil. I formed the coil by filling the lenght of copper with dry sand (I think it was bagged dried sandbox sand from a home center), crimped the ends of the tubing (leaving room to cut the crimps off later) so the sand couldn't escape, and then wrapped it around a metal 3 pound coffee can that was filled with cement to firm it up. The coffee can was just right for a loose fit on the 6 inch stovepipe.

Here's a real short article that relates to this thread:
http://www.hearth.com/what/woodstovedhw.html
The illustration shows using a pump and controller if the tank and coil can't be arranged for gravity circulation.
And another site with useful info:
http://www.woodheat.org/dhw/dhw.htm
And I just found this through Gary's BuildItSolar.com site:
http://www.michigan-horse.org/preheater/


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## ET1 SS (Oct 22, 2005)

Michael Kawalek -
You have a Monarch wood cookstove with a hot water reservoir that produces hot water.

Rather than running water through it, you wish to 'adapt' it by running a coil of copper tubing inside the reservoir to absorb heat from the hot water that it is making.

Build a fire, to heat water, then refuse to allow that water to flow, rather transfer secondary water through the heated water, and hope for heat transfer from the heated water over to secondary heated water.

Yes, you can.

In fact, I would say that you have a right to do that scheme.

Better yet; try this. Once you have transferred heat from the primary heated water to heat a secondary flow of water, then you could take that water and run it through a second heater exchanger. Heating a third source of water.

You can screw with a perfectly functioning hot-water system as much as you wish. 

"My first question is how hot does the reservoir water actually get? Can I expect 120F or 210F water. How long does it take to get hot? If hot, how many feet of copper tubing will I need to absorb the heat?"

It gets as hot as you heat it up to.

Circulating water through it will slow down it's heating.

To tear apart a perfectly functional hot-water heater to modify it with copper tubing, could take as much copper tubing as you wish to throw at it, or as little.



"A second idea is instead to wrap copper tubing around the stovepipe exhausting the stove. ... "

I have wrapped stovepipe with tubing myself, it worked well. We did it to a pot-belly stove.

A commercial on-demand propane fired water-heater, uses about 30 foot of tubing in a coil around a flame.

Our current system uses 50 foot of tubing.



On question though, what is wrong with the Monarch? Since it is a hot water-heater, and since you can plumb it's inlet and it's outlet to anything you wish to plumb them to, what exactly is stopping you from using it?


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## RayG IA (Jan 22, 2008)

I'm looking at a backup for my electric hot water heater here in my trailer. I was thinking about getting a propane hot water heater, water pump and pressure valve out of a wrecked RV. Connecting this up to even a 55 gallon barrel would give me water for several days. I could refill the barrel by running the generator. If I had a 500 gallon tank, it would last a couple of weeks at least.


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