Basement getting smoked out

[u/LostTwo4794]

Hello. I have a stack with 3 flues. Two fireplaces and one furnace. When I turn on the top fireplace in the first floor my basement gets smoked out. Any tips on why this is happening ( I believe theres a break in the flue) and thinking about doing a wood insert with a new vent.

We only really use the first floor fire place too so it’s constant. The smoke is worse in the beginning but I think it’s more then just a cold flue because I’ve tried to start the basement fire first to warm up the flue but it still gets smoked out

Im getting a cleaning done and want this done before winter as i use the finished basement. I attached a picture

All help/opinions are welcome. Thank you

[u/Lots_of_bricks]

Likely stack effect more often than cracks in the flues allowing smoke to traverse between them. Stack effect is the homes pressure differential and the outside conditions. Installing a top mounted damper system on the basement fireplace usually stops this issue. But if u do not intend to use it then save money and seal the top of the basement flue with some metal and silicone.

A wood burning insert and liner will be a great addition to the upstairs fireplace but it can potentially still have the same issue with smoke falling down the basement flue if u don’t seal it.

[u/LostTwo4794 → u/Lots_of_bricks]

Thanks for the reply. I hope Thats it. I might get the extender for the upstairs first and hopefully that gives it enough clearance. We go through a lot of wood upstairs so I think the stove will be more efficient anyways

[u/Lots_of_bricks → u/LostTwo4794]

Try just sealing the top of the basement flue 1st. Extenders dont always work, won’t work with the insert/liner system and can be expensive. An seal the top of that flue for less than 20$ and can easily remove if necessary

[u/ThatllBtheDayPilgrim → u/Lots_of_bricks]

I reread that he doesn't really use the basement, he could stuff something up the basement flue from the fireplace (free) and see if that works for now.

[u/Lots_of_bricks → u/ThatllBtheDayPilgrim]

Be better to seal at the top tho. Would ensure the smoke was actually from the top and not traversing a gap in the tile liners.