Backdraft through Hot Water Chimney

[Rancher22]

I have my Woodstove in the basement, with the chimney (6" rigid liner) going through an external brick chase. Also in the same chase is the 5" chimney for the hot water tank.
What's happening is, depending on the wind direction (seemingly) the smoke is coming out the stove chimney and then some is getting sucked back down the water tank chimney and going into the utility/furnace room.


Counsel I was given was to extend the stove chimney by 2-3', and as well to swap up the cap for something called a "Vacu-Stack".
The theory being that the cap will strengthen upward draft so smoke clears faster, reduce the chance of wind forcing smoke back down, and make it less likely for exhaust to spill across into the (now comparably lower) water heater pipe.

I have 2 questions for you experts regarding the above:

1. Does this seem like a reasonable solution? And if so...
2. Do we recognize this brand of stainless steel liner?

It uses twist-lock to connect the male/female ends. The only markings I can find on it read "Made in Canada" and "000000"
Most options up in here Canada are Selkirk, DuraVent and ICC, but google image doesn't seem to show a good match.

And for the record - I do plan to brace the new higher stack to either the roof or brick chase itself.

Thanks in advance!!

 

[Whitenuckler]

View attachment 340345
I have my Woodstove in the basement, with the chimney (6" rigid liner) going through an external brick chase. Also in the same chase is the 5" chimney for the hot water tank.
What's happening is, depending on the wind direction (seemingly) the smoke is coming out the stove chimney and then some is getting sucked back down the water tank chimney and going into the utility/furnace room.

View attachment 340342
Counsel I was given was to extend the stove chimney by 2-3', and as well to swap up the cap for something called a "Vacu-Stack".
The theory being that the cap will strengthen upward draft so smoke clears faster, reduce the chance of wind forcing smoke back down, and make it less likely for exhaust to spill across into the (now comparably lower) water heater pipe.
View attachment 340344
I have 2 questions for you experts regarding the above:

1. Does this seem like a reasonable solution? And if so...
2. Do we recognize this brand of stainless steel liner?
View attachment 340343
It uses twist-lock to connect the male/female ends. The only markings I can find on it read "Made in Canada" and "000000"
Most options up in here Canada are Selkirk, DuraVent and ICC, but google image doesn't seem to show a good match.

And for the record - I do plan to brace the new higher stack to either the roof or brick chase itself.

Thanks in advance!!

For the hot water tank...is that a gas unit with a blower? If so the blower should never allow a reverse draft.

 

[begreen]

The problem is that both terminate at about the same height. If the gas unit's flue could be lowered by 12" that would help reduce the back-siphoning. Otherwise, raising the wood chimney by 12" will help. Hold off of the vacustack until trying this first.

If negative pressure can be reduced in the basement by sealing house leaks, that will also help.

I don't recognize the chimney pipe. Make sure it is class A insulated for the wood heater. Also, where are the storm collars?

 

[Rancher22]

For the hot water tank...is that a gas unit with a blower? If so the blower should never allow a reverse draft.

No, it is not a power vented hot water tank.

The problem is that both terminate at about the same height. If the gas unit's flue could be lowered by 12" that would help reduce the back-siphoning. Otherwise, raising the wood chimney by 12" will help. Hold off of the vacustack until trying this first.

If negative pressure can be reduced in the basement by sealing house leaks, that will also help.

I don't recognize the chimney pipe. Make sure it is class A insulated for the wood heater. Also, where are the storm collars?

If I lower the water tank, it'll stop just below the level of the brick chase, so I'll have to raise the other. Why hold off on the vacu-stack, it's simply not needed?

And again, it's stainless steel rigid liner, not Class A.

 

[Whitenuckler]

If you have an oil fired boiler (same as was in this house) providing your domestic hot water, then it would seem
to me the burner is not drafting correctly, and that needs to be solved for safety issues. Mine is decommissioned
when they got off oil. The domestic hot water is now electric, which you could consider. If you are heating your house with it, then no.
My furnace room is vented to provide fresh air. I use that now for my pellet stove OAK.

 

[begreen]

No, it is not a power vented hot water tank.

If I lower the water tank, it'll stop just below the level of the brick chase, so I'll have to raise the other. Why hold off on the vacu-stack, it's simply not needed?

And again, it's stainless steel rigid liner, not Class A.

Have a WETT inspection of both flues. In the US, an uninsulated chimney pipe is not approved for wood stove operation. It must meet high-temp, 2100º, class A spec. Gas appliance venting require B-Vent chimney pipe here.

 

[Rancher22]

Have a WETT inspection of both flues. In the US, an uninsulated chimney pipe is not approved for wood stove operation. It must meet high-temp, 2100º, class A spec. Gas appliance venting require B-Vent chimney pipe here.

It has passed WETT inspection

If you have an oil fired boiler (same as was in this house) providing your domestic hot water, then it would seem
to me the burner is not drafting correctly, and that needs to be solved for safety issues. Mine is decommissioned
when they got off oil. The domestic hot water is now electric, which you could consider. If you are heating your house with it, then no.
My furnace room is vented to provide fresh air. I use that now for my pellet stove OAK.

It is a propane hot water tank. The drafts just fine when heating up, but that only a few times per day. When not in use, it's "normal" (I'm told" for there to be a slight vacuum in sub zero temps, much like opening a door or window.

 

[begreen]

It has passed WETT inspection

OK, if it passed inspection then it's likely in a full masonry chimney as a rigid liner. I'm not sure who makes it, but the brand is less important with single-wall if adding an extension as long as the diameter is the same. Maybe ICC?

ICC Rigid Stainless Steel Liner Lengths - 6" Inside Diameter

Friendly Fires stocks and recommends ICC EXCELiner rigid stainless steel liner system for many different applications. ICC Rigid Stainless Steel Liner

friendlyfires.ca

 

[Whitenuckler]

It has passed WETT inspection


It is a propane hot water tank. The drafts just fine when heating up, but that only a few times per day. When not in use, it's "normal" (I'm told" for there to be a slight vacuum in sub zero temps, much like opening a door or window.

I had one of those Natural gas power vent ones before and didn't like it. It was noisy and needed power to run. Plus all the extra parts that could break down. It would be an option for you though if your present one was old or breaks down. That would get rid of that side of the chimney. Also, the electric hot water tanks are good. It sounds like you don't use much hot water which a small electric would supply.Ifyou only use propane for hot water then you might eliminate that bill. Most people use it for other things though.
Adding that extra chimney piece may not always work depending on where the smoke from the fireplace ends up due to prevailing winds.
It looks like it's fairly easy to get to the chimney on your house, so it's worth a try to extend.

 

[Rancher22]

I've added the extension and Vacu-Stack cap to the woodstove.
Although it feels fairly solid and is still under 5' from the stone work, I may get a brace for it regardless.

If there's still any smoke backdrafting down the lower hot water tank chimney I may grab a directional wind cap for it as well, but I'm hoping this makes the difference. I'll give an update either way in case any others have a similar issue.
I

 

[Whitenuckler]

I've added the extension and Vacu-Stack cap to the woodstove.
Although it feels fairly solid and is still under 5' from the stone work, I may get a brace for it regardless.

If there's still any smoke backdrafting down the lower hot water tank chimney I may grab a directional wind cap for it as well, but I'm hoping this makes the difference. I'll give an update either way in case any others have a similar issue.
View attachment 340677I

It looks good. I hope it solves your problem, and thanks for the update!