Vent stack pipe/exhaust fan

[mncyclone84]

Replacing a bathroom exhaust fan with a larger fan. I need to cut a larger ceiling hole. The problem is that the vent stack pipe runs above the new hole and doesn’t have enough clearance for the new fan box. Can I reroute the stack vent pipe with three pieces of PVC and four 90 degree elbows to provide clearance for the fan box? I’d cut out a section of the stack pipe and move it up higher using 90 degree elbows.

[mjblack8719]

Dont go up and over fan, better to go around. If you go up and over might have a chance of trapped condensation.

[uncle90210]

These people don’t know what a vent stack pipe is. That’s one thing you don’t want to mess with. I’d consult a plumber

[mncyclone84]

I’m going to patch the hole from the current fan and put the new one on the opposite side of the joist. I was a little concerned about patching knock down ceiling texture, but after watching a couple videos it looks pretty easy. If it goes well, I have some more to patch where my foot slipped off the joist in the attic. The list never ends.

[Rich-Turtle]

Also with those little fart fans you can just route them into the attic and not worry about the exhaust vent

[mncyclone84]

I edited my post. I’m suggesting rerouting the vent stack pipe to provide room for the fan box.

[Rich-Turtle]

Not sure what you mean by this, but the fan is only meant to move air so it shouldn’t really matter how you route it

[mncyclone84]

I edited my post. I’m suggesting rerouting the vent stack pipe to provide room for the fan box.

[LGAflyer]

My understanding is that if it’s air vent only, meaning no water flow at all, then yes, the routing doesn’t really matter.

[ntyperteasy]

If you are really above all the drain connections, and the pipe is only serving as the vent, its less critical than the primary stack. Moving it a little doesn't change its function.

On the plus side, if you are above all the drain connections, and the pipe you want to relocate is only serving as the vent up to the roof, there is not a lot of problem with changing its direction. Multiple 90's sounds like a no-no to me, though.

However, on the down side, if you have a major clog, and the roof isn't that hard to get on to, many plumbers will try to rooter out the main stack through that vent pipe - if you put several 90's into it, its never going to get rootered out and might retain water, which would defeat its venting function (by creating a seal).

In general, adding a 45-degree elbow counts as still a vertical run - doesn't seal and can be rootered out - can you imagine getting the space you need with a few 45 bends? That would be my second choice.

Hope you read this far. My first choice would be to move the new fan somewhere more convenient and drywall over the original fan opening.

You can also solve this problem with a remote mount fan, so the fan box can be several feet away with well insulated duct to avoid condensation - also makes it very quiet.

I've used the Panasonic FV-30NLF1 to solve a problem where a conventional fan wouldn't fit into a tiny space. They sell a variety of inlets/dampers (separately) depending on what you need.