Water heater tank next to stove - no insulation!

[Billy_Bob]

I had to change my initial plan to use old steam heating radiators next to my wood stove to pre-heat the hot water for my hot water heater.

The problems with the steam heating radiators is that they had chemicals used in them to prevent rust (don't want reminants of this in my hot water), and without the chemicals in the radiators they would likely rust away on the inside (like using black pipe), and steam heat radiators are designed for about 20 psi (water pressure) whereas city water pressure can be 60 psi.

The problem which brought all this to my attention was when I plugged the radiator and connected it to the garden hose and water went spraying out everywhere!

Anyway I changed my plan... (If at first you don't succeed, try, try, try again!)

I took an old 50 gallon electric water heater and removed all the coverings and insulation from the tank. Then removed the dip tubes and heating elements. Then plugged all the holes except the bottom drain connection and one top connection.

Then I painted the tank black (black in theory will collect more heat).

Next I placed this tank right next to my woodstove. I am in the process of re-routing the cold water going to my hot water heater through this tank. The cold water will go into the bottom connection and warm out the top.

It looks quite promising so far. The tank next to my woodstove is too hot to touch!

Also this hot water heater tank says it was tested to 300 psi.

I'll post an update when I get it connected.

Note: I'm also installing valves to allow air to escape when filling the tank (goes to line which goes outside) and a valve/line to drain the tank from the bottom.

 

[user 19670]

Sounds like you have a winner. It appears to work much better than the old time "tempering tank".

 

[ray benson]

You might consider replacing the anode and the relief valve. Cost would be about $30 - $35.

 

[oneoldbanjo]

I am curious to see if the tank will sweat and drip water off the outside of the tank in cold weather. I would think that cold tank would cause the warm moist air to condense on the side of the tank - however it may be that after the initial filling and heating the water inside may never again be cold enough to be a problem.

 

[Billy_Bob]

Update: It works!

Actually it works better than expected.

I got my final connections made yesterday, then turned on the water. It was cold outside, so had a nice fire going in the woodstove.

After about two or three hours, I used some hot water at a sink (caused water to flow in pipes), then went and felt the pipes pipes going to the tank by the woodstove. The pipe going into the bottom of the tank (cold city water) was of course very cold. But the pipe at the top (water leaving the tank) was not cold! Felt about room temperature.

Feeling the tank... The bottom of the tank was quite cold and the top of the tank was not cold (but not warm).

This is a 50 gallon water tank. The water coming from the city supply is about 40 degrees (F) and quite cold. And I would say that the water coming out of the top of the tank was about 70 degrees (F) or about room temperature.

So with just a few hours of warming, I have 70 degree water flowing into the cold water side of my electric hot water heater instead of 40 degree water!

This morning after warming all yesterday and through the night, the tank was just barely warm to the touch all over (top and bottom).

So this should take a load off my hot water heater.

As to the condensation, I did not feel any on the tank itself. I did feel condensation all along the cold water pipe going to the bottom of the tank (40 degree water from city).

As to the anode rod and T&P valve, thank you for posting that. I had no idea water heaters had anode rods! But a quick visit to google.com and I now know all about them. So I will certainly get a new anode rod. I'll also get a T&P valve and drip pan. I didn't want to get these things until I saw if this idea was going to work or not. Anyway I'll now install it like a water heater would be installed to code. (Drip pan, T&P, strap it down to wall for earthquakes, etc.)

 

[nametrux]

Great!

Great Idea! That will surely cut down on your water heating cost.

 

[sredlin]

got any pictures of the setup?

 

[Ken05]

Great BillyBob - I have almost the same set up except I used an "extra" water tank from... My propane usage dropped about 25% when the woodstove is cooking. When both tanks are fully charged the shower lasts forever. Its great.

 

[Billy_Bob]

New Improved!

Well after a couple of days of testing this, I've decided to make some changes...

Actually this is working so good that I see a possibility for something more than just a water "pre-heater". That is to use the warm water for everything except showers. (Basically bypass the water from the "next to woodstove tank" so it flows directly to my hot water pipes.) And turn off my electric water heater except on shower days. (I don't take showers everyday during the winter to save on the electric bill. Summer is a different matter.)

One change I want to make is to raise the un-insulated water tank higher up. Currently it is sitting on the floor next to the woodstove. So the heat from the stove does not hit the tank at the very bottom. So I will raise the whole tank up about 10 inches or so. Then the heat from the stove will hit the lowest portion of the tank. This will also allow heat to circulate around the underside of the tank as I am going to use an old steam radiator laying flat on the floor and air will be able to circulate under the tank.

Also I want to install a "pre-pre-water heater"! That is I want to find a small water tank and run the very cold water in there first. Then into the existing tank next to the woodstove.

I think if I make the above changes, it will raise the water temperature in the pre-heating tank to a point that I could use it for everything except showers. Maybe a shower too! Who knows?

I also want to raise the electric water heater in the next room up so the top is a bit higher than the tank next to the wood stove. Then in theory the heat from the pipe on the top of the pre-heating tank should travel along this pipe all the way to the electric hot water "cold water inlet" keeping it warm.

Then I want to install valves to bypass the electric hot water heater and get hot (warm) water in the house plumbing directly from the tank next to the wood stove.

And I have a raised wood floor with crawl space under the house. I want to get under there and install some supports under all this. 450 lb. wood stove, 500 lbs. for pre-heater tank, 90 lbs. for old radiator to elevate tank, then more for pre-pre-heater tank, etc. Don't want it all to go crashing through the floor!

I'll post some pictures when I get it finished.

 

[panhead9]

I would instal a T&P valve it is still a pressure vessel. just to be safe

 

[MJC]

New Improved!

Well after a couple of days of testing this, I've decided to make some changes...

Actually this is working so good that I see a possibility for something more than just a water "pre-heater". That is to use the warm water for everything except showers. (Basically bypass the water from the "next to woodstove tank" so it flows directly to my hot water pipes.) And turn off my electric water heater except on shower days. (I don't take showers everyday during the winter to save on the electric bill. Summer is a different matter.)

One change I want to make is to raise the un-insulated water tank higher up. Currently it is sitting on the floor next to the woodstove. So the heat from the stove does not hit the tank at the very bottom. So I will raise the whole tank up about 10 inches or so. Then the heat from the stove will hit the lowest portion of the tank. This will also allow heat to circulate around the underside of the tank as I am going to use an old steam radiator laying flat on the floor and air will be able to circulate under the tank.

Also I want to install a "pre-pre-water heater"! That is I want to find a small water tank and run the very cold water in there first. Then into the existing tank next to the woodstove.

I think if I make the above changes, it will raise the water temperature in the pre-heating tank to a point that I could use it for everything except showers. Maybe a shower too! Who knows?

I also want to raise the electric water heater in the next room up so the top is a bit higher than the tank next to the wood stove. Then in theory the heat from the pipe on the top of the pre-heating tank should travel along this pipe all the way to the electric hot water "cold water inlet" keeping it warm.

Then I want to install valves to bypass the electric hot water heater and get hot (warm) water in the house plumbing directly from the tank next to the wood stove.

And I have a raised wood floor with crawl space under the house. I want to get under there and install some supports under all this. 450 lb. wood stove, 500 lbs. for pre-heater tank, 90 lbs. for old radiator to elevate tank, then more for pre-pre-heater tank, etc. Don't want it all to go crashing through the floor!

I'll post some pictures when I get it finished.

Pictures? I want to do something similar. How is the system running 14 years later?

 

[Del_]

Pictures? I want to do something similar. How is the system running 14 years later?

Last seen Oct 4, 2013

 

[Mike Van]

If you really want to save $$$$$$$$$$ - get rid of the electric water heater - There can be no greater waste of electricity than having 40, 50 gal or more of hot water sitting there being kept hot 24/7 so someone can wash a few dishes or take a 5 min. shower.

 

[MJC]

Last seen Oct 4, 2013

Thank you, Del_: Too bad.

 

[Patrick62]

You have a great idea going there, but I would make one modification.
It would be difficult for you unless you have access to a decent welder tho...

I use a "heat exchanger" in my flue pipe. Setup as a thermosiphon. A 3/4 pipe in at the bottom to a TEE, pair of 3/4 by 1" elbo's and about 16" of parallel pipes back to another TEE at the top. It all screwed together, but rather than use a union, I just cut and welded in the second pipe... I could make a drawing, I don't have any pics,. I think you get the idea tho.
Then use heavy radiator hoses to the hot water tank, top and bottom. I can see some very high temperatures off this thing.
a constant fire, and I will have way, way over 140F water...

Before this setup, I used to use a old cookstove that had a heat exchanger built into it. That was really overkill... A few times I went for a shower and was blessed with live steam...

You could do the same basic thing, and with 50 gallons you would have sufficient storage, it would not get as hot.