How to build a long burning rocket water heater with a used gas water heater?

Want to make a hydronic heater. The hot water will be circulated through radiators to warm the house.

A used gas-fired water heater, I have removed the gas valve and burner, now I have access to the fire tube, a straight tube with a swirling flue baffle inside.

A 55 gallon steel drum with a tight sealing steel lid.

Is the following design correct for a long burning rocket water heater?

I want to add a drum of wood in the morning, and have it fire for 24 hours.

How to control the burning rate of this rocket stove?  

A few things.....

Metal in the riser.  Won't last long with a hot fire.

Water in the tank will suck the life out of your fire, making it impossible to get good clean combustion.

You would need safety valves to insure you don't blow yourself up.

I am using an old nat gas water heater tank as a means to pre-heat water for my main water heater by means of a solar thermal collector, and by means of a copper coil buried in a bell bench.  So I'm only running heated water through the central fire tube and I plumbed it with threaded fittings for that purpose.

Thomas Tipton wrote:A few things.....

Metal in the riser.  Won't last long with a hot fire.

Water in the tank will suck the life out of your fire, making it impossible to get good clean combustion.

You would need safety valves to insure you don't blow yourself up.

I am using an old nat gas water heater tank as a means to pre-heat water for my main water heater by means of a solar thermal collector, and by means of a copper coil buried in a bell bench.  So I'm only running heated water through the central fire tube and I plumbed it with threaded fittings for that purpose.

The riser is the original gas fire tube and maybe some stove pipe extension, so it is already fire rated, right?
Yes, the water heater has T&P valve that can release extra pressure.

How to get a clean combustion before the fire reach heat exchanging surface?  Is it possible by making a longer fire tunnel between 55 gallon drum and water heater, and add preheated secondary air tube along the fire tunnel?

I once saw a fellow simply burn wood under his old nat gas tank, he managed to heat water.  I can't say it was very clean, or efficient.  I probably shouldn't assume that's a primary goal of yours.  For many stove builders here on Permies, it is a big concern.  

But no, a longer burn tunnel probably will not improve the situation.  If anything, raise the base of your hot water tank up above the level of the horizontal burn tube, maybe you'll get enough draft to get good combustion but I still feel this configuration is going to produce a lot of creosote.

Good luck.

Thomas Tipton wrote:I once saw a fellow simply burn wood under his old nat gas tank, he managed to heat water.  I can't say it was very clean, or efficient.  I probably shouldn't assume that's a primary goal of yours.  For many stove builders here on Permies, it is a big concern.  

But no, a longer burn tunnel probably will not improve the situation.  If anything, raise the base of your hot water tank up above the level of the horizontal burn tube, maybe you'll get enough draft to get good combustion but I still feel this configuration is going to produce a lot of creosote.

Good luck.

simply burn wood under his old nat gas tank : will it burn continuously for 24 hours?

Hate doing that, because the hot water tank is a bit heavy, and I don't have a winch/crane to lift it up, have to break back, and then step on a ladder to work on the plumbings and flue pipe.

Will a flue draft fan or intake air blower help with anything?

Just looked at my converted nat gas water heater.  Looks like the "riser" pipe that runs vertically up and down the water jacket is about 4 inches in diameter.  I'm assuming yours is the same. If so that would make it a 4 inch system.  Not going to create a raging fire.  You also may struggle to get it lit, depending on the temperature of the water in the jacket to begin with.  Considering that flame tube is subjected to oxygen rich flames when in normal use, I dare say in combination with the lower temperatures you should expect from a 4 inch system you might just get away with it.  You might try a heavily insulated and slightly extended burn tunnel, as your water jacketed riser is definitely going to put a damper on combustion after that point.  I would think an ash cleanout in front of and beneath your vertical feed tube will might make it easier for you to get it lit with an extended feed tube as you can just push your starter fire deep into the throat.  Depending on what kind of shape your knees are in.  That wouldn't be for me.  Lol.  I'm trying to keep everything where I can reach it from a chair.
Keep us posted.