Venting question

Now that we have installed our new Hitzer 50-93 its been 4 weeks since my
central heating system has come on.
With winter fast approaching I'm starting to worry about the pipes in the cellar freezing. We get down to -20 at times.
I have a propane fired water heater located in the cellar that has its own 8x8 masonry flue with a 6" round clay thimble.
I have an old coal chubby that I want to hook up.
Can I vent both into the same flue
Thanks,
Rick

you're not "supposed" to. one of the main reasons for the rule of flues only exhausting the same fuel is for combining a woodstove with another appliance, in the case of a chimney fire there would not be an effective way to shut off the air to the chimney. however, since you are not using wood, but anthricite coal as long as the chimney is in decent condition and the size of the flue can handle the volume of exhaust gases (and being an 8/8 tile flue it can) i would connect it. bear in mind the code nazi's may post after me and try to dissuade you from doing that, however, if your concerned not with code, but purely with safety and draft, provided the chimney is in decent condition you will have a perfectly fine setup.

Thanks for the quick reply
And sorry for the wrong forum post. Sometimes you can't see the forest for the trees.
The flues are part of a massive 3 flue chimney, and the draft will suck the hair off a tennis ball
Built this log home my self and have been down the road with the code boys
This is just an interim measure as I plan to power vent the water heater next year and use the flue for the stove only.
Regards,
Rick

I grew up in a home with an 8" flue in a brick chimney and we had a gas water heater and a coal furnace vented into the same flue no problem. I assume your water heater has a 3" or 4" flue. The water heater should actually vent better with the coal furnace. Just make sure you have a barometric damper on the coal unit and set the draft properly. It should be fine.