New breaching & flue liner?

ratio

Well, I've got to move the water heater in the basement to make some more room. The chimney & footer is in the center of the house, the water heater is on one side & I want to move it to the other side. I can get the wet core machine from work & core appx 12" through the chimney into the flue—is there any reason why I can't/shouldn't do that? I can also raise the breaching somewhat, right now I've only got about 8" from the top of the draft diverter to the breaching.

The inside dia of the flue is ≈ 7½ x 11½. I'm sure this was adequate for the old gravity furnace, but I'm down to just a water heater in that flue now, 33k input. I think this is a good time to think about a flue liner as well. Height to chimney cap is ±30', straight shot. Is there any reason to not install a 3" or 4" insulated flue liner since I'm already going to be doing some major rework? The flue seemed to be in fine shape the last time I was on the roof, maybe two years ago, several years into the current config (just the WH in the flue).

Tinman

Yeah, I'd do it in a heartbeat, no reason not to. 7 1/2" x 11'' for a water heater only? Your chimney will be raining down acid rain on the brick which will eventually be eaten up without the liner.

ratio

Thanks. Any recommendations re flexible double wall vs B pipe? I should be able to shoot hard pipe right down, but then I came across this stuff, Z-FLEX Insul-liner (pg 6), which seems like it'd do a bang-up job of it. But maybe it's way too much?

Tinman

I've done it both ways, mostly with a flexible liner. It's easier and less expensive and works just as well. With b-vent, you have to be able support it so that the 90 degree elbow you use at the bottom to get out of the brick chimney is not bearing the weight of the stack.

ratio

That's about what I figured. Have you seen that insulated stuff in use before? It sounds like it'll really help the draft.

Tinman

I have not. If helps keep the stack temp where it should be, it's worth looking in to.