how much fall for horizontal run?

[jotul?]

Now that my thimble is installed, I decided to check the fall on my horizontal run through the wall. Because I am a boneheaded brick layer, I automatically made my 3 ft. Horizontal run dead level. How important is that 3/4 inch fall that I knew to put in but didn't?

 

[begreen]

It does make a difference, especially with a rear exit. How tall is the chimney? Can you shorten the vertical?

 

[jotul?]

No vertical. Boss didn't want to see any pipe, so we're straight out the back.

 

[begreen]

No vertical. Boss didn't want to see any pipe, so we're straight out the back.

Not good. How tall is the chimney. Can you lower the hearth?

 

[jotul?]

Chimney will be 24 ft. No modifications possible but to move the thimble. If I have to do it anyway, should I go for a full inch of fall?

 

[begreen]

Oy, with 24 ft it may work ok, but could be a bit balky on start up until the flue is warmed up. Hard to say. If there's a problem it will be most noticeable on startup and reloading in milder weather. Once it gets cold and the stove is burning 24/7 it should be less of an issue.

 

[jotul?]

Thanks for the info. It's going to bother me, so I might as well move it and be done. I hate things that don't work properly. I don't have the interior drywall finished yet, so that's something at least.

 

[begreen]

Just to be sure, you want a 1/4" per foot rise in the horizontal run from the stove to the tee. 1" won't hurt.

 

[AtomicDog]

I just knocked out part of a block wall for the same reason. I was more worried about liquids not draining back into the stove than I was draft. Now that it's done I'm glad I did it. I also knew it would bug the crap out of me if I didn't change it.

 

[jotul?]

I want to say thanks to begreen for his info. I moved the thimble last night after work and I feel much better about my install. I also bought a piece of Kaowool to insulate around the thimble before I close the wall up and install the interior cover plate. No sense cheaping out on the safety part. $70.00 is a pretty inexpensive piece of mind. I've used that stuff to do refractory repairs on hot coke ovens, and it stands up to 3000 degrees on a working oven for days at a time. It makes me feel better to know its between my combustibles and my flue gasses.