thoughts on using galv water pipe in a woodstove?

Discussion in 'Homesteading Questions' started by raymilosh, Nov 14, 2005.

  1. raymilosh

    raymilosh Well-Known Member

    Messages:
    635
    Joined:
    Jan 12, 2005
    Location:
    NC
    hi all
    I built a solar and wood fired water heater for myself...i followed all the safety rules and it is working well. My waterjacket is an expensive welded stainless steel tank ($280).
    Now i'm building one for a neighbor. I'd like to build a less expensive waterjacket for installation inside the woodstove. I was planning on using flexible copper and hiding it behind a steel plate in the firebox so it wouldn't be damaged while wood was being loaded into the stove.
    I'm wondering if I build an exposed galvanized set of pipes if it would be easier, cheaper, stronger and better at conducting the heat, as it would be exposed directly to the fire, rather than from behind a plate. I'm wondering if screwed together galvanized water pipe would develop leaks at the threads if it were installed inside the firebox of a woodstove.
    The water in the pipe will be under standard house pressure, by the way.
    Does anyone have any thoughts or experience?
     
  2. Alex

    Alex Well-Known Member

    Messages:
    833
    Joined:
    Mar 20, 2003
    Location:
    Vancouver, and Moberly Lake, BC, Canada
    As stated by union creek, do NOT use galvanized pipe. USE Black Iron to reduce the cost. Arrange the pipe so you can remove and replace when required.

    Stainless steel pipe would be better, but of course, more expensive. Or, your idea about copper with a protective metal plate would be OK too. You do have a temperature pressure relief valve (tprv) in the system, on the hot side?

    Galvanized pipe is not allowed in any potable water system by any plumbing code. The Zinc that enters the potable water tends to kill people. Though, of course, for years nearly all plumbing pipes were galvanized. Also, I suspect heating galvanized pipe in a cookstove could realease zinc, just like welding sheet metal, and neither procedure is good.

    No galvanized would be my vote,

    Alex
     

  3. mtman

    mtman Well-Known Member

    Messages:
    2,260
    Joined:
    Sep 2, 2004
    Location:
    AR
    it does give of a toxic blue smoke and the threads will not be coated they are cut in after the hot dipping it allso will rust and restric the water flow thats what i think
     
  4. Ross

    Ross Moderator Staff Member Supporter

    Messages:
    13,086
    Joined:
    May 9, 2002
    Location:
    Ontario
    If black iron is used and the water kept sealed from air it will only rust until the solution is saturated (black) and then stop. I had noticed galvanized presure tanks were disappearing should they be removed if in use!???
     
  5. TnAndy

    TnAndy Well-Known Member Supporter

    Messages:
    5,427
    Joined:
    Sep 15, 2005
    Location:
    EastTN: Former State of Franklin
    I've used black iron as a grate in my fireplace, running the water to a 500 gallon tank in the basement, and then to hot water basebd registers, for the last 20 years.

    Make the pipe the smallest diameter you can, and get the most you can in there to increase your surface area. You could use it as a grate in the stove a few inches above the base and build the fire directly on it.
     
  6. Alex

    Alex Well-Known Member

    Messages:
    833
    Joined:
    Mar 20, 2003
    Location:
    Vancouver, and Moberly Lake, BC, Canada
    Ross:

    Hard to say if you should replace a galvanized pressure tank. There are still a lot of galvanized pipes and other items around in older drinking water systems. It is a good idea to take it out.

    If money is OK then why not take it out and put in a bladder tank?

    Good luck,

    Alex
     
  7. WisJim

    WisJim Well-Known Member Supporter

    Messages:
    2,180
    Joined:
    Jan 13, 2004
    Location:
    WI
    Where is galvanized pipe not legal? I wouldn't use it in a stove where it could get real hot, but it is still commonly used for potable water in the USA. I work with a plumber and a steamfitter who are very current with code changes, and we are still using galvanized pipe. Of course, we use a lot more copper because galvanized is such a pain to thread etc.

    My in-stove water heating coils were made with black pipe, and I have had no problems over the years.
     
  8. raymilosh

    raymilosh Well-Known Member

    Messages:
    635
    Joined:
    Jan 12, 2005
    Location:
    NC
    Thanks for the replies, everyone. I have always heard to use galvanized because black pipe would rust too quickly. Hearing that it oxidizes to form a coating and then stops sounds reasonable enough.
    I am aware of the health hazard of welding galvanized through experience and from prefessional welders. I was originally thinking it would be alright in the woodstove because as long as it contained water it couldn't get that hot, but if black pipe works, I'll just go with it.

    Alex, I'd also be interested in any more info you could point me to regarding Zn in drinking water.
    TnAndy, I'm interested to hear more about your system. Is there a pump to move the water from the fireplace to the tank in the basement, or does it thermo siphon. Is it part of a loop? Is the tank in the basement above or below the fireplace? Did you make it yourself out of threaded pipe? Did you have any problems with it leaking? I was thinking I had to put this system of mine on the wall of the stove in an "S" pattern so the cold water would move in from the bottom and flow out of the top as part of a thermosiphon loop to the tanks which would be above the stove in the attic. Can I get away with less than that?
    Also, did you conclude that smaller diameter pipe is best from having experienced problems with larger diameters?
     
  9. thedonkeyman

    thedonkeyman Well-Known Member

    Messages:
    699
    Joined:
    Jun 18, 2005
    We have wood heat and my thinking is to install a larger pipe around the smoke stack then have a coil of Copper hot water line between the two. The hot water tank is close by the stove on the back porch so we would preheat the water before going to the tank, which could be shut off. See any problem with this ? Also there is a side hill just behind the house, with a southern exposure where we could use a passive solar system to heat water in the Summer. More on that later.
     
  10. raymilosh

    raymilosh Well-Known Member

    Messages:
    635
    Joined:
    Jan 12, 2005
    Location:
    NC
    I didn't quite understand your situation well enough to have specific advice. General advice, however I can do.
    First, please buy a copy of "Heating Water from your Woodstove" from Lehmans.com.
    http://lehmans.com/shopping/product...RODUCT&RS=1&keyword=hot+water+from+your+woods
    It's about $12 with shipping. It is a 20 page book written in plain english by one of the Lehman family. It will answer all your questions and it will prevent you from killing or hurting yourself or your woodstove with a steam explosion. thee are a few stories of flipped over 600 lb woodstoves and water tanks rocketing through the roof.

    It sounds like you want to run the cold water line past the woodstove on the way to the water heater tank. If that's the case, it would turn to steam while you weren't using the water and the water would pass by too quickly to be preheated much when the water was flowing. A coil of copper inside the chimney pipe may work well if your chimney stays very hot, but the water would need to flow slowly through it at all times the chimney was hot, so it would have to be part of a loop. I considered doing just that, but thought there would be much more heat available in the firebox where there is both convected and radiant heat.
    Hot water rises. If your water heater tank isn't a bit higher than the woodstove, you will need to have a method of pumping the water from the stove to the tank. If it is higher, it will flow naturally (thermosiphon), provided you plumb it such that there is nowhere for bubbles to gather in the pipe and stop the water flow.
    I learned all of what I'm telling you (and lots more) from the book I mentioned.
     
  11. norris

    norris Well-Known Member

    Messages:
    101
    Joined:
    Dec 25, 2004
    Nothing better than hands on experience. Did you use schedule 80? What kind of thread sealer did you use? Have you had any problems with leaks? Have you always made sure to have water in the pipes (to prevent warping) while using the fireplace or doesn't it matter?
     
  12. TnAndy

    TnAndy Well-Known Member Supporter

    Messages:
    5,427
    Joined:
    Sep 15, 2005
    Location:
    EastTN: Former State of Franklin
    OK…..here’s the LONG version of Andy’s fireplace that heats his house. Typed it out once, but hit the wrong key and it disappeared….MAN, I hate when that happens…..

    I wanted to build a fireplace that would heat our entire house……I know a woodstove is way more efficient, but I LIKE a big open fire in a fireplace. Unfortunately, a typical fireplace is a net loss of heat generally, as it sucks room air up the flue more than it heats.

    First I set a metal “heat-a-lator” air circulating firebox in as I built the fireplace…didn’t use the fans cause I didn’t like the noise ( had them in a previous one ), but natural convection pulls air in the bottom vents, and lets it out the top vents.

    I had a welding shop build a set of ¼”plate doors and a face frame about 2” wide. I welded it in the fireplace opening. The doors just “clip” on the frame….I take them off when I build a fire…then when we go to bed, I load up the fire with wood, and clip the doors on so it doesn’t suck the room air up as the fire dies. Also have an ash pit that sucks outside air in for combustion.

    The fireplace is located on the main floor, and the only way I could figure to get wood to it ( if you gonna burn wood, and lots of it, you better figure out to minimize the mess up front ) was to built a 30” square shaft to one side of the fireplace, running to the basement. I mounted a 120v winch on an I beam in the top of the shaft ( all this is hidden behind the brick front ) and a ‘dumbwaiter’ car out of angle iron that I load the wood on in the basement, then raise to the first floor level. A counterweighted walnut door on the main floor level is the access.

    Then I wanted a water circulating grate in the fireplace so I could heat other parts of the house with hot water.

    The first grate I built was a couple of 3’ pcs of 4” steel pipe with the ends capped off and ¾” pipe welded between them…picture an “H” with more center pipes. It had some 4” legs to keep the grate off the hearth, and the fire was built right on the grate. Heated some, but not all that well.

    Next, I found a company out in Oregon that was closing out some “water grates”…so I ordered one. It was made of some steel tubing, bent in the shape of a “C” with a manifold across the top and bottom. It had a ¾ pipe adapter on each end of the bottom manifold….worked MUCH better…..but I figured out why when I put a calculator to it….lot more surface area in those smaller tubes….it had about 20 rows of tubing.

    Unfortunately, the tubing was too light, and it only lasted about 8 years. When that one started leaking, I built the next one using their design, with some modifications.

    I put the supply on the right end of the bottom manifold, and the takeoff at the top manifold on the right end. I often wondered if theirs was working right, with the supply AND takeoff being on the same manifold…..wondered how much would circulate thru the “C” loops, if any…..so I “force” mine to go thru the C tubes.
    Also, I use sch 40 black iron, which is a lot thicker than the tubing they used…and I made 25 rows of C tubes ( bent with a conduit bender...drilled the holes in the manifold, then took the whole mess to a pipe welder....I aint THAT good )…I’ve used it 10 years now with no problem. All connections of pipe thread are just sealed with teflon based pipe sealing paste...no problems with leaks.

    The takeoff line exits the manifold, turns a 90 down, then 90 again to run with the supply line out the side of the firebox and into the dumbwaiter shaft. I have a T in the takeoff line, and a screw in thermostat is located there to start a 1/4hp circulator pump when the fire builds and heat the water enough. Also have a manual override switch on the wall with an LED light to tell me when that pump is running……also a remote temperature sensor that has readings for outlet temperature, tank top and bottom temps, and outside air temp. A pop off valve is located just beyond inline thermostat…it dumps down the wood shaft if it pops off. Also, I ran a line UP the wood shaft to the top ( located on the second floor area of the house ) and mounted a small water heater tank up there for an expansion tank. When water is heated, it expands…..using a trapped tank of air lets the air compress, which the water won’t, and keeps from popping off the safety valve as the pressure rises. You need this in any closed hot water system.

    The circulator pump runs to an old 500 gallon propane tank in the basement, which is enclosed in a foam box. I tried a regular sheet metal fuel tank at first…..as soon as the pressure built a little, it split wide open and I had 500 gallons of water in the basement and tank that was scrap metal…..don’t go there….ahahahahaha……this old propane tank I got for 100 buck from the propane place because it was ‘too old’…..data plate on it says built in 1953 out of 3/8” steel and pressure tested to 450psi……has worked quite well for me now going on 20 some years ! Even had a top and bottom piped port, so I didn’t even have to weld on it….just plumbed it up and go. The fireplace circulator pump draws off the tank bottom and feeds back to the top as long as there is enough fire in the fireplace to make it run. I use another small pump to draw water out of the tank and run it around to baseboard radiators to heat the rest of the house…..it is controlled by a regular wall thermostat in the hallway…..though what I have found in practice, is unless it is real cold, there is plenty of thermosyphon action going on there, and the radiators stay pretty warm without the use of that pump.

    The fireplace itself is a massive brick and block deal…..probably 20 tons of masonary in it….took me 3 weeks to build..….once a fire is burned for a few days, it holds quite a few BTUs on it’s own…..and with a day or two burn, I get the tank temp up to 190-210 degrees…..500 gallons of water at 200 degrees is a LOT of heat……if the weather is not too cold, we can go a couple days without a fire coasting on that built up heat.

    Some changes I would make IF I would doing it all over:

    I’d use infloor pex tubing……that wasn’t around when I built the house in 84, or at least not like it is now.

    I’d use more storage……1000 gallon, or maybe more. Real easy to get 500 up there with the design of this grate. 1000 gallon at 160-180degrees is a LOT more BTUs than 500 gallons at 200 degrees.

    But overall, I like the system and am quite pleased with it.
     
  13. norris

    norris Well-Known Member

    Messages:
    101
    Joined:
    Dec 25, 2004
    Thanks for sharing that with us, TnAndy, you are brilliant. I agree it is nice to have a visible fire in a fireplace to watch, nothing like it. With all the wood on your place conserving firewood is not the issue, conserving your backbone is, which your dumbwater helps you to accomplish. Never heard of a system like yours. I like it. Good planning and lots of work sure can give you a lot of enjoyment for years.
     
  14. Quint

    Quint Well-Known Member

    Messages:
    3,510
    Joined:
    Nov 12, 2004
    Were were cutting scrap once and I got a big dose of fumes from galvanized metal. Gave me one of the most horrific headaches I have ever experienced and I felt like I had the flu. I was incredibly fatigued. All I wanted to do was sleep. Took a week or more for me to fully recover.
     
  15. MELOC

    MELOC Master Of My Domain

    Messages:
    7,220
    Joined:
    Sep 26, 2005
    Location:
    Pennsylvania
    wow. no wonder you were a little miffed. i hate when i lose my messege with the push of a button.
     
  16. Arborethic

    Arborethic Well-Known Member

    Messages:
    186
    Joined:
    Oct 16, 2005
    Location:
    Texas
    I would suggest that anyone considering using galvanized pipe or tanks read this first: http://www.anvilfire.com/iForge/tutor/safety3/

    I've built coils for water heating in fireplaces and wood stoves in decades past. I always used STAINLESS STEEL piping! It can be bent using a pipe bender, and sometimes judicious heating for the tighter radius bends without much trouble.

    Another thing, you MUST install a pressure relief valve!!!!! Or you risk blowing the system up and sending shrapnel in ever direction.