issues with venting to chimney pipe...

Discussion in 'Cannabis Grow Rooms and Greenhouses' started by fourtwozero, Jun 23, 2006.

  1. fourtwozero

    fourtwozero Member

    'm starting a grow room in a corner room in my basement. the chimney pipe for the house is not far from the room, so I plan on venting the room into the chimney. i figured i would get a 6" inline fan, and run a 6" flexible duct over to where the chimney pipe pokes through. however, there are a couple issues i'm not sure how to solve:

    first, a gas furnace and hot water heater are venting into the chimney, and the points where they join into the chimney vent are not very far away from the point where i would have to join my flexible duct to the chimney pipe. is there any risk of blowing toxic fumes into my house from venting my grow room like this?

    second, where is the best place to install the inline fan? at first i was thinking i would install it in the grow room and "push" the air down the flexible duct and into the chimney. however, it seems that installing the fan further down the line and "pulling" the air out of the room would be a better idea. the only problem is that, again, the hot water heater and furnace vent into the chimney pipe in close proximity to where i would have to install the fan... so once again, am i going to be blowing toxic fumes into my house? or, if i install the fan further downstream to "pull" the air out of the room, will i run the risk of pushing the air out of the nearby hot water heater vent and stinking up my basement?

  2. buffoonman

    buffoonman Senior Member

    Can't see why there should be a problem as your pulling air out of the grow room and venting into the chimney. How would fumes get into your room?
  3. Naturalhi

    Naturalhi Great hairy ape

    I'd be more worried about blowing air the wrong direction, into the appliances. How world you keep the air from blowing out standing flames and the flames from burners out of the fire box.
  4. buffoonman

    buffoonman Senior Member

    Oh you mean the pilot light.
  5. Naturalhi

    Naturalhi Great hairy ape

  6. Naturalhi

    Naturalhi Great hairy ape

    I didn't mean say that there isn't a way to make it work, if I knew more about or could see the situation I'd probly be able figger it out.

    "the points where they join into the chimney vent are not very far away from the point where i would have to join my flexible duct to the chimney pipe." After rereading I wonder is the place you want to connect on the end closest to the exit or are the app pipes closer to the exit, what diameter is the chiminy pipe, furnase pipe, and w/h pipe.
  7. fourtwozero

    fourtwozero Member

    thanks for the advice guys... let me see if i can describe the situation better:

    my grow room is about 10-15 feet away from the place where i can access the chimney. so, i will run flexible ducting from the room to the chimney. the place where i can access the chimney is basically a big 3-way junction of pipes. the first junction comes from the gas furnace, the second junction comes from the hot water heater, and the third junction used to go to the wood furnace, but since that was removed, it is now just capped off (and this is where i will tie my flexible duct into).

    the thing i worry about is the hot water heater. the junction that comes from the hot water heater is about 3 feet of 2" pipe, and then that flares out over the top of the hot water heater. there's about an inch gap between the end of the flared pipe and the hot water heater. i'm not sure why it's designed that way, but it is. so, if i'm blowing things the wrong way, i could potentially be blowing my stinky weed smell in a reverse direction into the hot water heater (which would probably stink up my house, or even worse, blow nasty fumes from the hot water heater into my house). is this something i should be worried about, or will it never happen?

    i've been thinking about this for awhile, and i think the safe way to go would be to install a duct fan in the grow room, and then install another fan at the 3 way pipe junction, to suck all the air up the right way. the only thing is, i really wanted at least a 6" fan and a 6" flexible duct, but my chimney pipe is only about a 4" pipe. so it will take a good bit of modification to install even a 4" fan there... but it seems like that will be a bottleneck either way.. any ideas?
  8. Naturalhi

    Naturalhi Great hairy ape

    Still need more input; Chiminy, I'm seeing a brick chiminy that runs from basement to roof, yes no? if yes whichever connection is closest to chiminy use that for room exhaust, now in the connection point instead of the T connector install a Y connector _\_ like so connect hose to angled pipe toward chim this should create a flow away from w/h- furn, rereading this it's almost as clear as mud if it's unclear maybe I'll figger out a better way to describe it in a minute!
  9. fishheadbob

    fishheadbob Member

    I'm unclear. If the wood stove exhaust was only 4 inches it is awfully small. But if it is, most wood stove shops, hardware, farm stores carry all sorts of reducers and expanders to make one size pipe compatible with another. For a few bucks you can make a 4" pipe fit a 6". Seems like you could fit whatever size blower you wanted wherever.
    Water heat vents are designed that way.
    Toxic fumes are a real and serious concern. Real serious. I'd want to test the daylights out of that setup before I started any plant, test with the furnace roaring (in July?). I dunno where to get smoke maybe a fireworks store, but some pretty red or orange smoke could give you some idea whats blowing where.
    Lastly and most importantly is 2 CO2 detectors. The more I think about it the more I think you're playing russian roulette.
  10. fourtwozero

    fourtwozero Member

    no, it's not a brick "fireplace-style" chimney.. the house doesn't have a fireplace, so the chimney is basically a 4-6" pipe that goes from the basement to the roof.

    fishheadbob, the smoke idea is good... i will probably try that. do you think my idea with the two fans will make this a safe setup, though? the first fan (in the grow room) would suck the air out of the grow room and into the duct, and the second fan (installed AFTER the y-junction with the hot water heater) would keep the air from the grow room flowing in the right direction.

    my other question is, if i use a reducer to get from my 6" flexible duct to the 4" chimney pipe, am i basically just creating a bottleneck that isn't doing me any good? in other words, would a 4" fan and a 4" duct do the same thing as a 6" fan, a 6" duct, and a reducer to a 4" duct? i know that a 6" fan will have a lot more CFM than the 4", but i'm not sure if that CFM is just wasted when you hit the 4" section of pipe.

    thanks for all the advice, guys. i'll let you know if i kill myself.
  11. fourtwozero

    fourtwozero Member

    btw, just in case it's important, the room is about 10'x9'x6.5' ... so 585 cubic ft. there's a window in the room that i plan on using for air intake.

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