# DC fittings



## _Ogre (Feb 1, 2013)

i'm just getting into dc system setup. i notice that a lot of people here insist that two 45° fittings with a short pipe between is better than a single 90° fitting of the same radius. anyone want to expand on this? from my research the static pressure drop calculation of a 45° fitting is half the 90°. three 90° or six 45° in the system would be the same calculation for static pressure drop. i spent a career welding and fitting boiler pipe and hvac duct and was taught the same. 2-45=90











i did spend quite a bit of time in furniture factories, where there were miles of dust/chip extraction piping into massive bag houses. i notice that all their branches came out of the top of the mains. my own whole house vacuum installation manual also recommended top or side for branch lines off the main. has anyone notice blockages caused by branch lines coming off the bottom?


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## Terry Q (Jul 28, 2016)

The secret to 90 degree bends is to use larger size duct work to the 90, then taper down to final size after the 90.

I have two branches in my current setup entering main duct from bottom at 45 degrees toward extractor, I see no issues with it.


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## DrRobert (Apr 27, 2015)

I do it, but I doubt it makes much practical difference.


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## _Ogre (Feb 1, 2013)

Terry Q said:


> I have two branches in my current setup entering main duct from bottom at 45 degrees toward extractor, I see no issues with it.


Good to know. I guess if you don't use a drop for a while, it could fill up. I really have no idea what I am doing, like everything else I'll just wing it 😂


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