Question on pvc drainage fittings

[Bill Jobe]

Why 2- 45° elbows seem to be preferred over a long sweep 90, other than about $10 cheaper?
Seems to me one long sweep would create less turbulence that 2 45s.

[Tom M King]

I don't know that it's really preferred. Probably just fewer parts to keep in the truck for that particular plumber.

[Jim Koepke]

Why 2- 45° elbows seem to be preferred over a long sweep 90, other than about $10 cheaper?
Seems to me one long sweep would create less turbulence that 2 45s.

$10 is a good enough reason for many folks.

If you are transitioning from a vertical to a horizontal run you may want a little more turbulence.

My knowledge of pluming is likely just enough to get me into trouble.

jtk

[Greg Parrish]

I’m assuming you mean for dust collection purposes and if so I used two 45’s because I couldn’t find any long sweep 90’s and the normal shorter 90’s that I could find had just that, a shorter turn. I’m not sure that a 6” pvc sewer fitting really sees that much air flow difference between the two but that’s why I did use the twin 45’s just in case.

[Tom M King]

Plumbing fittings are not only cheaper from a dedicated Plumbing Supplier, but they have a much larger selection, and can usually order something from their main branch that they don't keep in stock at that particular store. Save for HVAC ducting from HVAC suppliers.

[Larry Frank]

Two of 45s give you a little more adjustment if you need it.

I doubt that the two 45s give you better flow over even a shorter 90. The inside of the two 45s have several discontinuities that will result in a lot of turbulence compared to the a smooth 90.

[Greg Parrish]

Tom and Larry, both good points. On my twin 45’s I have used the joint between to get funky angles when needed. I have one straight 90 fitting and wouldn’t think twice about using it as I can’t say that I’ve noticed a big difference. Two things that make most air flow noticeable difference on my Oneida V3000 setup are keeping the filter cleaned out and taping over all the pipe joints to seal them up.

[Bill Dufour]

I read in the last year that two 45's flow less then one short 90. This is due to double the number of joints causing turbulance. Of course the long sweep 90 was best of all but not by much.
Bil lD.