PVC vs Styrene Drain Pipe Fittings For Attic Vent?

I'm hooking up a bathroom fan in the attic. I need to make a sharp bend
in the duct work, and had planned on using 4" PVC drain pipe fittings. I
went to Home Depot, and they have 4" PVC sewer/drain pipe (the thin wall
stuff), but all the fittings they sell are styrene. Other folks do sell
PVC fittings, but if I want to use PVC, I'll have to go hunting for them.

I was wondering what the group's feelings are about PVC vs styrene for
this. The attic is going to get toasty, and I would think the styrene
will get brittle compared to the PVC. As a matter of fact, I was reallly
surprised to see that they were using styrene at all for drain pipes.
I'm also not sure what sort of solvent is needed to glue the styrene to
PVC. I suppose they may assume the stuff just gets forced together
because it isn't under pressure, but that seems pretty odd too.
Doug White
Reply to
Doug White
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PVC for a bathroom fan? Why not use 4" aluminum ducting? Or insulated flex? Proper materials for the job? Greg
Reply to
Greg O
I'm using insulated flex for most of the run. My original plan was to use 4" aluminum duct joints for the bends, but the metal bends have lots of additional seams/joints, and that will cause drag. The biggest problem is that the bends go right after the fan, to get the duct up high quickly enough that most of any condensation will run out to the soffit vent. Using aluminum bends will take longer for them to warm up than plastic, producing more condensation in the one place it will tend to flow back down into the fan. If I use the insulated flex for the bend, it using a LOT more duct, or it has to bend too sharply, and it get's all kinky inside, increasing drag. Either way, a couple 4" PVC bends should produce a low drag, low condensation solution. Or at least that's my current theory.
Doug White
Reply to
Doug White
Ordinary tetrahydrofuran solvated PVC cement works fine for styrene fittings.
"Styrene normally isn't. Let's hope it's not. Most so-called styrene is a styrene-polybutadiene copolymer. It's a great deal more impact resistant than straight styrene, has better mould release properties, and doesn't shrink quite as much on cooling, which improves dimensions on finished parts.
Other than the butadiene component, there is seldom the need for a volatile plasticiser, so copolymer styrene parts tend to embrittle less with heat than "straight" styrene, which almost always requires a plasticiser. But styrene parts do embrittle relatively quickly. They'd be a bad choice in the attic.
Home JunkPot sells nearly only cheap Chinese crap, now. The styrene fittings are just plain cheaper than filled PVC. Go with PVC... a reputable brand.
Reply to
Lloyd E. Sponenburgh
What's wrong with aluminum smoke pipe?
Reply to
jim rozen

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