Getting rid of chimney - where to vent gas HWT?

We have a vented gas hot water tank that is currently using the chimney as a vent outlet. We want to avoid the cost of a direct vent unit, so we were wondering if there's a way of getting rid of the chimney (we're getting a new roof so now is the cost effective time to remove it) to save on heating bills (we live in an extremely cold area).
Is there a way to run a smaller vent up JUST for the hot water tank? I realize we need to run it UP so the gases accelerate as they go up, but how far up? I'm asking, wondering if we need to run it out the attic or if we can run it up and put an elbow in the vent higher up, say on the second storey and run it out the side of the house. We have a high efficiency furnace so that isn't vented out the chimney, ONLY the hot water tank uses the chimney currently.
The chimney currently is costing us a lot of money in heat loss, but we aren't keeping the house for more than a few years so it's not worth it for us to install a direct vented unit.
Sorry for the ramble, been gutting part of the house all day so I'm tired.
Dave
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You do not mention what country you in. Call your local building department to be sure. Where I live USA venting in attics is a severe no-no. We have to extend vented appliances above the roof line.
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snipped-for-privacy@gmail.com wrote:

<SNIP>
LOL I guess you didn't mean vent it *into* the attic, but rather extend up thru the roof in the attic.
That is allowed in **some** places, but you have to use double-wall pipe. In other places you can't even think about it. Ditto for running up the side of the house.
Frankly, I think you are going to have waaaay more invested in time and materials than if you had simply installed a direct-vent or power-vent heater. Yeah, they're a little pricey but the install is soooo easy.
Maybe even consider a tankless (instant) water heater.
Jim
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Dave Here is what I've done. If the chimney is still good but much to big for the water heater alone, install liner. They make a kit of 3 or 4" flexible stainless liner and top cap. Drop the liner down fit the top so that rest of chimney is sealed and put cap on liner. I usually mortar the bottom in also, so you end up with a chimney within a chimney. Least work. I have also removed the masonary chimney and replaced it with a type B gas vent, you can regain some inside space and conceal the gas chimney within a slightly thicker wall. Much more work, nice clean look when done. New chimney must come through roof in our area it must also be equal to the highest part of roof. I have also had a power vented water heater, it worked good but never again. Just another source of noise inside the house another motor and control systems to keep up with. Simple is better. Besides you need some turn over of air within a house to maintain a healthy environment. So exhaust some up a properly sized chimney is not such a bad thing.
Tom
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Dave,
I don't have an answer for you, I'm writing to question your underlying premise. How does your old chimney make the house cold or inefficient? Why do you believe that the chimney is responsible for a lot of heat loss? Is this idea coming from the government, a local utility, local contractor?
Dave M.
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It would seem that the easy solution would be to simply seal up all fireplaces, pipe thimbles, or other connections between the chimney and the house interior. No heat loss, no labor or cost of chimney removal, no labor or cost cost of repair of house where chimney was, and no labor or cost of installing a new water heater vent. Don Young

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