Replacing pipe, stove to wall thimble

[homebrewz]

I'm going to help some friends replace their pipe from the stove to the wall thimble. A small section of pipe is corroded from rust. The inside section is a 3' run to an elbow, then a 5' run to an elbow, then out to a 90 degree T and a 16.5' length of stainless triple wall on the outside. While the draft is usually adequate, occasionally they have issues with smoke blow back. I was thinking of increasing the slope of the interior pipe. Check out the pics below. Any thoughts?

 

[begreen]

Can't hurt.

 

[Heatsource]

i'd maintain the 3' vertical off the stove, for sure keep at least 24" rise off the stove top before doing the offset

 

[homebrewz]

There's not a lot of room to play with in the current configuration, but I thought I'd solicit some comments anyway. I thought it was weird that they didn't go through the masonry until I looked at the outside. Thanks for the comments.

 

[RockyMtnHigh]

Looks like the outside run is pretty decent. I'd try to give as much slope to the inside as humanly possible. That is definitely not an ideal connector pipe run.... I'd try to figure out exactly why it's corroded/rusted. I'd go with something substantial like Simpson or Metal-Fab etc. No Home Depot tin metal stuff.

If you can move that stove to the left and maintain clearance etc. it would do you well. That is a bit much for a horizontal run even with a good slope to it.....