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Adding a septic tank with water for heat Storage????

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by airplanes20, Jan 5, 2012.

  1. airplanes20

    airplanes20 New Member

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    I have a Tarm Scandic Solo plus 40 and also have 2- 220 gallons of pressurized water in my basement now. I live in Thornton NH and on cold nights below 0 i only get like 6/7 hours out of a full burn cycle. My house is brand new with spray foam insulation (so i cant do anymore insulation). My basement is full and i have no more room for pressurized tanks (that would be ideal the 220 tanks are awesome).
    I have seen people put septic tanks in the ground and put loops in the tank. I didn't know if anyone on here has seen or used this method. If anyone has any information and you would like to share please let me know.

    How long of loops did you run?
    How big of a tank?
    Did you line the inside of the tank?
    Did you insulate the outside of the tank?
    How did you connect it into the boiler loop?
    Pics?

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  2. stee6043

    stee6043 Minister of Fire

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    Tanks in the ground are less than optimal. Earth is one big heat sink. Based on the experiences I've seen on this website the insulation and waterproofing will be rather expensive and highly critical.
  3. flyingcow

    flyingcow Minister of Fire

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    What am I missing? Just reload the boiler? BTW, how big is your house?

    On cold nights, like tonight I have to reload boiler.
  4. flyingcow

    flyingcow Minister of Fire

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    BTW...IMO a septic tank for storage is really not a great idea.
  5. BHetrick10

    BHetrick10 Member

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    I have been known to think out side of the "Box" sometimes a little to far.

    I was just thinking the other day about putting a HX in my actual septic tank when the boiler temp drops. Have a loop on a aquastat that when the storage gets so cold if a fire hasn't been made to circulate water through the actual septic tank. For obvious reasons I would want a loop going from a heat exchanger in the tank to another one that the boiler water would go through so if is does leak or erode it wont contaminate the boiler water or drain you system into the septic. Septic tanks seem to be nice and toasty between the warn water and other things that go into them plus the bacterial reaction.

    :cheese: How far out of the box is that?
  6. maple1

    maple1 Minister of Fire

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    That's way out there...
  7. Gasifier

    Gasifier Minister of Fire

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    Would a septic tank be inefficient? I would not want a tank in the ground myself, but am curious as to it's efficiency, or lack of.
  8. OT_Ducati

    OT_Ducati Member

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    if the septic tank was insulated well, above ground wouldn't the concrete mass add to the heat storage??
  9. joemeintzer

    joemeintzer New Member

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    If you wanted to have a remote tank why not have it pressure rated and forget loops? I say an LP tank would do it. Insulating would be more challenging.
  10. flyingcow

    flyingcow Minister of Fire

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    i don't see where the amount of storage is the problem. If he's burning 6/7 hours and can't charge storage and heat the house? how big is house(heatload)? What kind of wood? how long has wood been seasoning? When he's done burning, is storage charged to the max? Need more info.
  11. Gasifier

    Gasifier Minister of Fire

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    For the number of nights it will be that cold, sounds like the easiest thing to do would be the reloading of the boiler. If the whole system is pressurized and the wood is seasoned well, I am assuming the limitation is proabably the size of the burn chamber. If you did have more storage. Would you be able to heat it with the demand of the house and anything else that demands it, like DHW?
  12. maple1

    maple1 Minister of Fire

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    +1. I'm not understanding how more storage will extend burn times.
  13. in hot water

    in hot water New Member

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    It's tough to keep the heat in a tank buried in the ground. Any ground water, even rain run-off will wick away the energy very quickly. I have tried buried concrete septic tanks as solar storage, even with an expensive 4" of foam on all sides it was not a very efficient heat storage. i'd move that type of installation to the bottom of the list.

    I have also tried concrete tanks above ground, in my own shop actually. They do require a liner as the thermal expansion causes hairline cracks. It also developed a smelly
    bacteria of some sort when it cooled down in the summer.

    But it did end up making a nice water trough for the cattle.

    I'd be more inclined to build a super insulated building, maybe an ICF building to house an above ground tank. At least you could keep an eye on things and make adjustments and modifications. Plenty of nice un-pressurized "kit" tanks on the market.

    hr
  14. 711mhw

    711mhw Feeling the Heat

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    What is your storage temp. at the end of your burn cycle? If your home is as insulated as well as it sounds, with a good temp. of your storage, your storage should carry you thru the rest of the night. It sounds like you just need to play around with your operation of your system, that is when cold nights are expected, start charging your storage earlier in the evening and head in to the night with a head start. This, from a guy with no storage, but it's how I understand storage to work.
    How are you heating? (radiant, air...)
  15. Gasifier

    Gasifier Minister of Fire

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    What is your storage temp. at the end of your burn cycle? If your home is as insulated as well as it sounds, with a good temp. of your storage, your storage should carry you thru the rest of the night. It sounds like you just need to play around with your operation of your system, that is when cold nights are expected, start charging your storage earlier in the evening and head in to the night with a head start. This, from a guy with no storage, but it’s how I understand storage to work. How are you heating? (radiant, air…)

    This is a good point 711. I try to get my 400 gallons of storage up to 180 °F before I go to bed. If my wood runs out in the boiler before I get up the tank takes over and carries me a few hours more. It isn't until the aquastat on the tank gets down to 155 °F that the other fuel kicks on.

    airplanes20, Just out of curiosity. How are your tanks insulated? What temperature do you usually have them at when they are at their hottest temperatures? I am also curious about your spray foam insulation for your house. You must be pretty air tight. I have spray foam in my garage and love it. What type of air system do you have in your house? Did you have to install something that would keep humidity at a certain point? Is the spray foam in the walls and the ceiling of the top floor? Just curious. I heard at one time that if your house is too air tight with the spray foam that you might develop a problem with humidity that could lead to mold. I have never seen that, but did hear that a guy had a problem with his house being to air tight. I don't have to worry about that with my house. :lol: I have some places that are insulated fairly well and some that are not fairly well. :lol:
  16. Tennman

    Tennman Minister of Fire

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    Horrible idea. Coefficient of thermal conductivity of generic concrete = .7, rigid polyurethane foam = .018-.02. Concrete transfers heat about 40 times faster than a foam insulated vessel. Now if you blew foam on that septic tank before you lower it in the dirt.... just kidding. But really just dig a pond and heat it, about the same performance.
  17. Two words.

    "bore holes"

    http://www.dlsc.ca/borehole.htm


    Just takes a few years to get up to temp,but then you can just coast for the next decade!
  18. stee6043

    stee6043 Minister of Fire

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    Hah....ohh man, sometimes these things are real mind benders!

    I can't even imagine what kind of WILD growth you'd get in a septic tank if you kept the temps above 100 degrees on a consistent basis. This aside from the comments above really suggesting the efficiency of this setup would be horrible at best.

    No need for ridex!
  19. rkusek

    rkusek Minister of Fire

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    Septic tanks are for poop. That would be like saving money on installing faucets in your home by just dipping your drinking water out of the toilet.
    My local NRD (rural water system) sent me a questionaire about what kind of interconnections I have:
    1. Do you have a sprinkler system?
    If yes, is it protected by a testable backflow prevener?

    2. Swimming pool or hot tub?
    If yes, is it protected by a testable backflow preventer?

    3. Boiler heat or water to air heat pump?
    If yes, it protected by a testable backflow preventer?

    It won't surprise me now when they add the question below.

    If yes, does your boiler plumbing come in contact with your poop tank or lagoon? If so, we may need to check it for leaks because that would make our drinking water taste like chit!
  20. BHetrick10

    BHetrick10 Member

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    This thought came to me after I read articles on some of the huge dairy farms that collect methane and are "Green in operation" pulling BTU's out of there holding tanks is something they've done. It was a really neat article. Collected the Methane, used it to run water cooled generators to powers everything. The water that cycled through the rads went through HEX for heating the water. I have never seen tanks as big as those before. They were buried underground ans some where in the range of 50' wide 30' high 100' long. He referred to them as digesters. Had to maintain a certain temperature for the bacteria to produce methane he even added food scraps from local restaurants.

    I also worked in a very old house that had a big water tank in the attic. I guess they used the heat to preheat the water. If I remember correctly the tank was filled with sand, and the water lines passed back and forth through it a few times.

    I think as others have stated before. . sounds like a shed out back with some more storage in would be ideal if you cant feed it wood more often.
  21. airplanes20

    airplanes20 New Member

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    The house is 3000 sq ft, i have radiant in the basement, and forced hot water upstairs. I do put a full load on the tanks at night my last time out to the boiler is around 10-10:30, the tanks get up to around 180. I then wake up around 4:30 am and the tanks temp are down to 110 or so, i try to keep the tanks from going under 110. After i start the boiler in the morning it takes about 2-3 hours to be back up to 180. I am using seasoned wood, so i know thats not the problem. I just need more storage if i had another 200 gallons i think i would be all set, but like i said i don't have any room in the basement. Reading everyones post guess ill go another direction. Thanks for all the info
  22. airplanes20

    airplanes20 New Member

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    airplanes20, Just out of curiosity. How are your tanks insulated? What temperature do you usually have them at when they are at their hottest temperatures? I am also curious about your spray foam insulation for your house. You must be pretty air tight. I have spray foam in my garage and love it. What type of air system do you have in your house? Did you have to install something that would keep humidity at a certain point? Is the spray foam in the walls and the ceiling of the top floor? Just curious. I heard at one time that if your house is too air tight with the spray foam that you might develop a problem with humidity that could lead to mold. I have never seen that, but did hear that a guy had a problem with his house being to air tight. I don't have to worry about that with my house. :lol: I have some places that are insulated fairly well and some that are not fairly well. :lol:[/quote]

    The tanks have 2-3 inches of spray foam, when they are at 180 you can put your hand on the foam and its not even hot, so i know the tanks are holding the heat very well. the houses has 2inches of spray foam with an R-11 bats. Gives my walls an R28 but i didn't need and air purifier like your talking about. I have heard the same thing from people. The guys that insulated the house told me if i had put 6 inches of spray foam in the wall i would need the purifier installed.
  23. flyingcow

    flyingcow Minister of Fire

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    have you done a heat loss calc? that will give you a better idea than just throwing another tank at it. No doubt it would help, but you might need more than 200gals. I have a baseboard complimented by my kitchen that is radiant. My radiant is staple up and I have to keep the water about 135/140 in the deep of winter to keep the floor warm. But that being said, I have a set back thermostat on BB heat, because if it stays set in the 70's at night I loose alot out of my storage. same goes during the day when no ones home, T-stat sets back during the day. i drive my 820 gals of unpressurized storage up to about 175ish at night(by 9pm) let the fire go out, thats after starting it about 3pm. The other night it was -7 with a 10 to 15 mph breeze. We had to do a fire again by 7amish to get thru the day because my wife was home. I live in a 1800sq/ft, 2 story house, on a hill, in northern Maine, that has average insulation. By no means not as well insulated as yours. My unit is an Innova-30, a little smaller than yours.
  24. maple1

    maple1 Minister of Fire

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    It sounds like your boiler is outside, and your storage is in your basement? Is that right?

    Seems to me that you're losing a lot of heat somewhere - wondering if it could be between your storage & boiler? In my mind that much storage should last quite a bit longer than 6 hours with a full firebox and the house up to temp. My house is 15 years old, 2700 sq.ft. on two levels plus an unfinished unzoned insulated basement. My furnace is dirty & inefficient, with no storage except for it's own 30 gallon capacity, and I can make it from 10pm to 7am by loading full at 10 with the house up to temp. Things might be a bit chilly downstairs by 7am (downstairs gets set back over night), and the boiler is down to 140 or so, but I just have to rake the remaining coals and re-fill it with wood and away I go again.
  25. flyingcow

    flyingcow Minister of Fire

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    i think Maple1 might be on to something.

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